Loyalty points on purchases?

I’m aware that there is loyalty points functionality, but I haven’t discovered how to activate it and I presume that it only applies sales.
One of our suppliers gives loyalty points on our purchases. Does anyone have a suggestion on how to handle this?
Obviously, there is no calculation involved, since the number of points awarded is printed on the purchase receipt, but it would be useful to be able to record the number of points ‘in credit’, and to apply points to payments.
Failing that, I guess that I simply need to apply the points used in payment as an additional discount.