I usually crimp the crust (by pushing the dough, using my thumb and the first two fingers of the same hand...push the dough with your thumb into the space between the fingers), or, for a thinner crust, cut off the excess dough and firmly press the dough to the pie plate using the back of the tines of a fork. Be sure to press firmly so that crust doesn't shrink away from the pie plate. Good luck!
The way I do it is after fitting the bottom crust into the pie pan, I trim it with a sharp knive leaving about a 3/4" overhang all around. Refrigerate for 20 or 30 minutes before filling. After filling the pie, I brush the edge of the bottom crust with water then place the top crust (also refrigerated) trimming to a 3/4" overhang. Then pinch the edges of the two crusts firmly together. If the doubled edge seems to be too thick, just squeeze it out a little with your fingers and retrim to maintain a 3/4" overhang. Then fold the doubled edge under itself so that it's flush with the rim of the pie pan. You can then crimp or flute the edge with your fingers or with the back of a fork. On apple pies I like a high fluted edge to help keep the juices from overflowing. I simply use my fingers to do the fluting. Here's a video demonstration: