Maybe you haven't installed it properly, you have to put the ESF-Bot.dll in the dlls folder of esf. Then you have to change a line of code in a file called liblist.gam in you main esf folder.
change the last line from
gamedll "dlls\hl.dll" to gamedll "dlls\ESF-Bot.dll".
now as far as choosing which character the bot comes out as i think it's totally random even if you put in a character name but i'm not sure so just type addbot.
Be aware there are a few bugs, the bots can move while transforming or recharging, they're aim is a little off at times, they attack each other as well as you regardless of the team they are on, and they don't always know when they should recharge and will sometimes get stuck trying to do the same attack over and over again, also sometimes when they do actually recharge they can't stop.
That's about all the bugs i've noticed