move the poke'ball around with the mouse pointer, and when its touching 1 of the pokemon then click or press space and then you have caught it.To catch mudkip you must use the dive ball.To switch you're ball to the dive ball press right arrow, to switch back to the pokeball press left arrow. Up arrow and down arrow to change size.
My credits are to @amphoros thats it! Also it should say scratch would like to acess your camera so if you press OK then the background will be you!