Character select by custom buttons


Can someone give a tutorial link or usable keywords to find help about character select by custom buttons (or images ) i want to make something like baldurgs gate/ dungeon siege like game,where you controll a party with different characters

Already working with press 1-2-3-4 on keyboard, and they are all following the main character but dont know how to use custom buttons to get controller for the specific character,anyone can help/ send a good tutorial / or only give some keyword for this to google it?

Thanks for help!