When you put the screen on hold the ipod with the top to your left and long ways. Take the glass and tilt it up from the bottom about 15 degrees. Push the top in first and work your way gently down to the bottom. You should feel the screen "snap" in place.
When your first starting out, do this several times, without the adhesive on, to get the right feel. At this point you can check the iPod, if there are any issues, you can easily remove the screen, fix the problem, and re-check. Once everything runs ok, lay down your adhesive and insert the screen as described.