Like in straight flight, you can turn in a slip with aileron and rudder.
But in most planes you will need full or nearly full rudder to keep
the plane slipping, so only the aileron is left to control a turn.
Use it as you would use it in straight flight.
You only can do rather wide turns.
I prefer to to slip with the nose pointing to the outside of the turn
(i.e. left for a right turn).

There is one PROBLEM:
The indicated airspeed is close to zero, so you can only control the
airspeed by observing the angle between your plane and the horizon.
You will need some training to do this for any specific type of plane,
especially in mountain areas, where the horizon image changes during turn.
So it is necessary to try first at high altitude and it with an instuctor.
Be shure that you are trained to do straight slips, and to recover from a
stall.
For a real landing, you should use it only if a normal landing with flaps is
not possible.

By the way it is big fun!
Walter