There are 2 commonly seen methods for juggling clubs above the head, the clubs can either be thrown with, or without, spin.
Hold the clubs with the handles pointing forwards, and put your hand more or less under the club's centre of gravity. To throw, push straight up with your whole arm, and if you need extra height then use your fingers just as the club is launched. This trick is easier if juggled with a small, fast pattern.
If you can already juggle 3 above your head using floaters, then use the same grip for this version of the trick, i.e. catch the clubs near the centre. If you can't do it on floaters then you will probably find it easier to catch them in the middle of the handles, and use a lot of arm movement to impart the spin. Make fairly high throws with slow spins, and keep the pattern slightly wider than your shoulder width. This is one of the most dangerous 3 club tricks to do, for obvious reasons, so be prepared to run immediately should anything go wrong.
To go from a cascade to above the head, throw a single reverse spin out of the pattern to above your head, carrying the other 2 up in your hands.