Place the new wood door on two sawhorses. This will make it easy to reach the door, but you will need to paint one side of the door and then when it dries turn the door over to paint the other side.
Spread latex painting primer on the new wood door. Roll a short nap paint roller into the primer and then roll it on the door. Use a paintbrush to reach into small areas on the door that can’t be reached with the paint roller. Let the primer dry as long as the manufacturer directions recommend.
Paint the wood door with latex paint. Again, use a paintbrush to paint details on the door and a paint roller to cover large areas. Wait for the paint to dry and repeat. Let the final coat of paint dry overnight.
Install the door in place per manufacturer directions. Install a door knob with a screwdriver.