The Warden is a keystone of security tasked with managing the Brig and everything within it. This ranges from making sure detained prisoners are treated with respect (or at a minimum, not beaten to death), to overseeing and (in emergencies) distributing the contents of the Armory.
The Warden answers directly to the Head of Security and indirectly to the Captain, but generally anyone else inside the Brig answers to the Warden as long as they are there. As the Warden, you're often the thin red line between the Armory and any number of trespassing threats; ranging from a sticky-fingered Clown to a Traitor looking to bust their buddy (or assassination target) out of the Permabrig.
The Outside World
The Warden is strongly discouraged from leaving the brig for any amount of time over a few minutes. This can leave the highly volatile contents of the armory, rowdy prisoners looking for a way out, and confiscated contraband unattended, thus giving someone a chance at grabbing it without being noticed. The Warden is also very strongly discouraged from helping themselves to the contents of the armory without reason -- this puts a terrible look on you and is generally completely unnecessary. It generally just paints you as someone who took the job for quick access to as many guns as you can carry and further increases the value of beating you up in the hallways if you leave for some reason.
A Warden outside of the brig is also an extremely high-value target for anyone out to pilfer ID cards or equipment; perhaps the most dangerous item you can lose is your ID card which gives its holder unrestricted access to everything in the armory. Not only does it give them as many guns as they want, they can give their friends guns too. And their friends are probably not your friends.
My Rifle, My Gun
The coveted Armory is usually one of the most-secured places on the station, second usually only to the Captain's Quarters or other sensitive areas of the bridge. Depending on the station, it usually contains 2-3 each of laser rifles, pump-action shotguns, submachine guns, spare shotgun shells, lethal and non-lethal ammunition, security hardsuits, bomb suits, portable flashers, and more.
This is quite a massive list of equipment to keep track of, but generally, if you are doing your job right, it doesn't move often without you knowing about it. As the Warden, you are expected to safeguard this equipment and prevent unauthorized access at any cost. The only other people that should be allowed in and out of the armory is Your Boss and Your Bosses' Boss. You should discourage them from taking everything they can carry, but try to avoid arresting them on the spot.
You should absolutely prevent anyone from getting into the armory who invites themselves in without good reason and isn't the Captain or Head of Security. Heads of Personnel cannot typically resist the allure of hitting the all access button on their own ID and may think that entitles them to grab things from the armory as they are the "captain's right-hand man", but unless they've gotten approval from someone you answer to, you shouldn't just let them grab whatever they want.
It is also your (and the Head of Security's) discretion on when the contents of the armory should be distributed to your Officers (or, god forbid, the crew). Station threats like carps and spiders are much more safely handled if you can hand a competent officer something lethal, it can just be challenging to find that competent officer under your command. Otherwise, your officers are left with non-lethal means only and usually have to beat the enemy to death with a baton, exposing them to greater danger.
Folsom Prison Blues
The second important part of your job is taking care of the brig and general security area. You should keep it clean, lock up contraband, and secure any weapons or equipment lying around in the open under lock and key. This keeps the place organized and makes it harder for an intruder or loose detainee to get easy access to weapons or equipment that have been left lying out by people who are lazy.
You also are tasked with keeping an eye on any detainees brought in by your officers. You should verify that they've been brought in for a valid crime, ensure they have been appropriately searched, make sure they have any major injuries treated to, make sure any contraband is confiscated and secured, make sure an appropriate sentence is given (officers will often look to you for sentence advice), and make sure the detainee is released with all of their belongings (minus contraband!) when their time is up.
This is a lot to do, but essentially you just need to watch over and make sure that your officers are doing a good job and not power tripping too hard, while also making sure the detainees aren't forgotten about. Officers will often leave prisoners in your care while they go back out on patrol, so depending on how proactive they are, they may dump a detainee on you without saying anything and leave just as quickly. Make sure they explain what actually transpired or actually brig the person themselves.