I'm not that good.
But do a search on youtube. There are a bunch of good instructional videos from simple wrist shots, snapshots, slapshots, back hand shots, and some of the trick demo's like that 9 year old kid.
Also, do a search for the video's Kovalev made for WArrior sticks. He does one where he shows how he uses the sticks flex to shoot the puck.
Lastly, just practice on the ice as much as you can, saving the slapshot last as that shot is used the least in a game.
I'm around 5'7 but I weigh more than 130 lbs. Try an intermediate stick. They might end up being a tad short for you, in which case you can added a wooden extension onto it to get it to the right height.