Stand the glass pane upright on your work bench resting on a good smooth 2 by 4 for full glass support. Spray the glass and the butyl strip with lots of soapy water, spray the metal clip with soapy water. Make sure you orientate the clip in the correct direction for a right, or a left window. The clip goes in the center, not critical, but close to center is OK. Use a large rubber, leather, or plastic mallet to hammer the clip on to the window pane. Don't worry about the excess seal. Set the assembled window glass pane out in the sun for a day to get hot and dry out. Use a single edge razor blade to trim the excess seal "when it's cold" which is much less messy. It's maybe a five minute job, super easy. You do it the same way on vent windows.
John