Lost steering, control arm fell off steering knuckle..

I'm not too familiar with the names of these parts so i'll do my best to explain it...There are two little knuckles where the steering comes down into the front end, the control arm came off one side so the wheel and tire swings free..is that joint a press fit back onto the ball?? I've got another four wheeler for parts I just need to know the basics on replacing it, I can' t figure out how why it fell off or even what holds it on the ball in the first place. now when you turn the handle bars it turns the one side but the other side isnt' attached to the steering anymore....

rookie questions I know but if I could fix it myself instead of spending money that would be great....