You've picked a not too fun project for your first
You will need some 1/8" nylon cord, cord that runs the drapes in the house works great if you have some of that.
First put the seal on the glass, place the string in the grove in the seal overlapping at the bottom. With you on the inside, have a helper place the window in the hole bottom edge first, getting the string ends inside. While the helper is pushing on the glass slowly pull the string end toward you pulling the seal edge over the lip of window frame, do one side then the other until you get all the way around the window, as you get further along the helper may need to do some flat handed slapping on the glass to help get the seal to seat.
Here's a couple of links on windshield installs, this is the same way old style windshields were installed. Hope this helps
Windshield Installation FREE Instructions