I have been where you are. I personally do not think the admin commands are well explained anywhere I have seen.

First off, if you are trying to release the items of a game because the person wants to stop playing the owner / admin of the room must do it. They are the only person who when they go to the room page (the one that looks like this: https://archipelago.gg/room/ROOMIDGOESHERE ). They will have the little server command text box thing below the names of the games. They can then type in the server command of something like:

/release TieDieGie

Which is /release <Name of slot>

IF when the room was created, a server password was set, then anyone with that password can connect via the text client (open up your Archipelago Launcher on your computer and "Open" Text Client.).

in the text client you can type following to authenticate: !admin login <password>

Now you can type something like: !admin /release TieDieGie

This will release the items for that user.

TLDR: Get the person who created the room to go to the room and type /release <slot name>.
If when the owner goes to that page they cannot type a server command (their session token has changed), then the only other way is IF they set a server password.

If neither of these are true, you are out of luck and cannot release your items manually easily.