The admin menu is where the magic in all games happen. If you are the owner of a server, or playing by yourself, this key lets you do everything.

First thing first is binding it.

I believe by default the bind is Numpad - however can be changed via
Options > Binds > User Interface/HUD > Admin menu
Personaly i use "P" for it.

To use the Admin menu, start up a local game.
Once in, deploy and press the respective bind to open the admin menu.

These are the supported game modes:

• Domination
  
• Firefight
  
• Skirmish
  
• Outpost
  
• Team Death Match
  
• Push
  
• Range
  
• Checkpoint
  
• Frontline

NOTE: Range as far as i was told does not work as of now.

When changing and the bots do not appear, their is a work around.

Open your console
(To bind the key, go to Options > Binds > Console)
Type this:
Bot
This will possibly add the bots.

If the bots do not appear, try the admin menu.
I don't know if this works, i assume its like TF2 and most games that run off of source.

If you want to change the bot limit, here is a discussion:
Click this dummy

NOTE: Please be carefull modifying files. The anti-cheat may see somthing wrong and you could get banned. i'm not liable for this, so don't cry to me if it does happen.

Good job, you figured out how to add bots. Now enjoy this wikipedia article about AI being stupid:

Click here dummy[en.wikipedia.org]