First of all what coin are you using to practice with? Use a half dollar, they are the best for coin tricks, and once you learn to palm that you will be able to work down to smaller coins.
In terms of technique, rest the coin on the tips of your second the third finger while your palm is up. Go to turn your hand palm down and curl your fingers into a fist. The coin should naturally be pushed into the 'sweet spot' where is can be held by the muscles. In terms of getting your hand the look natural that will come with time. After time you will realize that the fingers don't play a part in controlling the muscle that will hold the coin. A good exercise to build that muscle and to get used to having a coin in palm is to hold a coin there all day and use the hand as normal. I did this for years and still do use this technique.
Hope this helps, if you need anymore advice just message me, glad to help.