You can put the mint in the water, hot or cold, and it will infuse the water with its mintie taste. For tea you can put the leaves in a cheesecloth bag, or just put a couple on the cup [don't tear up the leaves too small if you tear them at all] then boil some water, and pour it into the cup. You could also put leaves and water in a pot to boil, or leave the mint in a container of water in the fridge overnight.
If you wish to use this in a magickal sense, cup your hands around the cup and charge it with energy, visualize a green glow around it [green for healing but I go for a light blue. Whatever works for you] or you could say a chant, breath deeply, and slowly enjoy the tea. Just relax and visualize your desired outcome.