If there is a slide in position and light from the bulb is visible but still no image on the screen, then the shutter may be damaged. You should switch to another projector. The bulb is burned out. The bulb can be changed, but precautions are necessary to minimize electrocution and hot bulb hazards. The bulb may still be extremely hot, so make sure it is cool before touching it.
Older projectors have a door on the bottom which can be unscrewed to provide access to the bulb.
There may be a lever to help pop out the bulb, but the older, tube-type bulbs can be difficult to remove and may possibly shatter. Newer projectors have a bulb assembly at the rear which slide out to give access to the bulb. A small metal lever will pop out the old bulb. Using the wrong bulb type can cause short bulb life, damage the projector, and be dangerous. There is some other problem.