Assuming you are using fresh mango, remove the mango flesh from the stone by cutting through the mango near the stone, on both sides, then scoring the mango halves. Pop open the mango and remove the cubes from the skin. Trim remaining mango from around the stone.
Put the mango flesh, lime juice and sugar in a blender and blend until smooth. Pour into popsicle moulds, leaving a slight gap at the top. Put in the sticks and carefully transfer to freezer, keeping upright. Allow to freeze - at least four hours.
Remove from moulds - put the mould under warm water if they don't come out easily.
For a slight twist on these, that's also very traditional, try a little chili powder in the mix or dip in tajin seasoning before eating.