I used to install auto glass here is how it goes... There will be a lip in the middle of the window gasket get a screw driver and unfold the lip out the glass be carefully not to break the glass as a screw driver is a substitute for a hook tool ( a screwdriver/pic with a curl on the end). Once you unfold the gasket have an assistant push the glass hard from the inside. Catch the glass and do not drop obviously. Tuck a nylon rope in the lip I described earlier. Then push the glass to the gasket. Make sure to push hard while the assistant slowly pulls the rope. The glass should slide in the gasket grove as the rope is pulled. Lots of glass cleaner will lubricate the window and the gasket. Hope this helps