Before you try to change directions (turn) you must be able to Water Start and ride both ways. A twin-tip board is best for this and it allows you to change direction easily. Reasonable wind (say 20 knots) makes changing direction easier.
Simple direction change
The easiest way to change direction is to:
* slow down at the end of a tack
* bring your kite to 12 o'clock and stop
* sink back into the water
* do a Board Start and head back in the other direction.
Sliding turn (also referred to as "Sliding transition")