There are two normal thread sizes fitting the ball head to the monopod. Normally it fit, or a small 'thread adaptor' is needed.
A ball head normally involves a base plate for quick release. It may come without. It is quite straight forward. Fit it before buying it if you are not sure.
Do some reading on the reviews. My serious advice - buy the best. Forget about the cheap stuff and compromise. It is meant to hold your camera still and safe.