To convert a screened porch into a winter porch takes a fair amount of time, materials and handyman skills. This is due to having to insulate, hang drywall and install windows in the space, among other things. To convert it temporarily, however, for guests or extra room during the colder months, takes only a little time and some knowledgeable handyman skills. Have a friend to help you set up everything and it should only take you an afternoon to accomplish, depending on the size of your porch.
Hang clear plastic around the inside of the three outer walls. Tape around the top -- snugly against the ceiling -- and pull the plastic down taut, before taping it to the bottom of the wall snugly to the floor.
Hang plastic over the outside doorway, if possible. If that is the only convenient entrance to your home, use draft stoppers underneath the door to seal out the draft when it is shut. Alternatively, hang a large, heavy curtain in front of the door to block out the cold that can be opened when entering the house.
Place space heaters in the room. One should be enough to keep it warm enough, if you live in an area with milder winters. Other options include a fan heater that is mounted directly on an outlet and a gas space heater. You may need more than one depending on the climate.