How an i get the interior light to come on when i open the door?

The switch may be in the door by the latch , maybe some cleaner would help free it up

It's either a piston switch in the jamb or a switch inside the latch. WD-40 or electrical contact cleaner might free it up. Otherwise, there might be a defect in the switch or wiring that needs a fix.

Try cleaning the switch first as "beatupchevy" suggested and if that doesn't work, replace the switch. Part is cheep and easy ti swap out.

It's either a piston switch in the jamb or a switch inside the latch. WD-40 or electrical contact cleaner might free it up. Otherwise, there might be a defect in the switch or wiring that needs a fix.