Right now it's hanging by electrical cords, believe there was some adhesive that came undone. I am not an electrician so don't want to mess with it. What is that adhesive called?
Those two screws you see protruding from the box are there to hold up the light fixture. Extend these screws to their full length so that they are in the electrical box, but are as long as they can get.
Remove the glass and possibly the lightbulbs from the fixture. You should see two slotted keyhole spaces that should line up with the screws. Push the screws through the insulation and into the big parts of the holes. Rotate the fixture so the screws end up in the slots.
Tighten up the screws, but do not over-tighten. Just tight enough to snug up the fixture to the ceiling.
Reinstall a light bulb, turn on the breaker and test the switch. If it doesn't work, then remove and check to make sure the wires are all attached correctly. They might have jiggled loose during this process.
Reinstall the glass.
There is no adhesive. Don't use any adhesive.
These all work a little different but basically you have your outlet with the two mounting screws sticking out, the plate, and the light.
The plate needs to be secured by the two mounting screws which seems to be the issue right now. It might slide in from a certain angle or the screws might have a nut (each) that came off on the other side. It looks like the plate and light are attached or somewhat at least. So you may need to unattach the light from plate to figure out how to get the plate on the mounting screws.