On TBC Karazhan server there is a feature to join any BG by typing ".join wsg", etc.

 

Is it possible for some plugin to queue this way rather than going up to the queue person? 

Lua.RunMacroText(".join wsg");

 

I'm pretty new to wRobot. Where exactly do I need to add the Lua.RunMacroText ? wRobot tells me everytime that I need to set the queue npcs. Do I have to write an plugin?

If that's what you want, yes you need to write a plugin or you can set up a macro ingame and use wrobot's macro settings to hit it every 30 seconds