Well, if you want to enter commands that give items into the client while playing on your own server (just like cheating in games) try this tutorial: http://fodev.net/forum/index.php?topic=29382.0
So, after you read all that text, you need to do the following to give yourself 50 bottlecaps:
1. Edit your getaccess.cfg and add the lines mentioned.
2. Restart the server.
3. After logging in, type: ~getaccess admin [password_you_set_in_getaccess_cfg]
4. Now type: `give PID_BOTTLE_CAPS 50 -p [your_character_name]
If you want to add items, you might want to do that by modifying the maps, you need to read the basic tutorials for it, as it has some pitfalls.