Simply mash/blend any fruit without skin & seeds of course. Add sugar and powder milk, this depends on how sweet you like them. You can also used cream or regular milk. Put them in a plastic container using a funnel (they call it "ice candy disposable bag" at amazon), make sure to leave about 2 inches off the top for closure. If you are good at tying them, you can probably get away with only 1 1/2 inch.
Below are mango flavor mixed with milk, that is they look light yellow instead of bright yellow.