Type: addbot <botname>
in your console.
For example, if you wanted to add the bot named "The Ghost" to your game, you would type "addbot ghost" in the console. You can run the "bots.cfg" file which has a pretty good load of bots in there.
Fritz doesn't run on mp_depot yet, I'm working on objective support ATM, and it will support depot in the future but for now you'll have to wait. The 3 maps that fritz supports have bots auto-load up for you. Fritz only plays capture point ATM, on the maps Destrution, Base, and TrenchToast.
Depot is my favorite RtCW map, so don't think it won't be supported in the future!
And yea, I know I need to make a bot menu that will let you do all this easier - its on the TODO list for this version.