To do this you have to be hosting the server.

1. Make sure you have enabled developer console.
2. Start offline game with no bots.
3. Join CT/T
4. Open console and type: sv_cheats 1
5. Type in console: bot_add t (or CT depends on your team, if you're CT choose T)
6. Type in console: bot_stop 1 (this will make all the bots standing still)
7. Type in console: bot_place (this will place the bot right in front of you, you can also bind this like so: bind "key" "bot_place")

Note: if you want to get on top of the bot use noclip (just type in console noclip and you can fly)

If you know any other great tips on this topic feel free to contribute. ;)
Also my english isn't perfect so if you find any mistakes please let me know.

My first guide: Useful Console Commands