Everyone has already given some very great resources on getting started, so I thought I'd offer a different piece of advice.
The success rate of being able to palm a card and get away with it is not dependent on the size of your hand. It helps to have bigger hands, but it by no means dictates whether you can do it or not.
Back in the early 1900s, there was a magician named Max Malini (if you stick around in magic long enough, you'll hear his name come up many times). He famously had ridiculously small hands; his hands were so small, he couldn't even palm bridge-size cards without it peeking. His student, Charlie Miller (another big name in magic), once asked him how he could palm cards and get away with it.
John Ramsay, a legend with small hands, sums up one point this way: "If you want someone to look at your hands, look at your hands yourself. If you want someone to look at you, look at them."
Charlie Miller asked Malini, Max, how is it you can always fool people with these sleights of yours?
Max replied, well, you don't do it when they are watching.
What do you mean? asked Charlie.
Well, take this side slip I do, Max replied, oh I wait I wait.
What do you mean by I wait I wait?
While I wait until they are not looking!
But how long do you wait?
Malini replied, I'll wait a week.
-https://www.finchmagician.com/blog/max-malini
Palming is not a matter of the size of your hand. Back when I first started magic, my hands were big enough to cover the whole card. Yet, I would continually get busted with the card in my hand despite the fact it was not visible. Palming entirely dependent on your skill in misdirection.
