I have a home that was built in the mid 40's. I have an outlet three prong on front wall I want to put an outside outlet just on the other side. I think I have purchased everything I need from Lowe's, so I don't burn the house down.. what can I worry about and can I use the existing indoor outlet to tap into.. thanks Jim

Sure, tapping into an interior outlet is fine, you should have an old work box or surface mounted weatherproof box, a short piece of cable of the same gauge as the inside wiring, a GFI receptacle, and a weatherproof cover.

Sure, tapping into an interior outlet is fine, you should have an old work box or surface mounted weatherproof box, a short piece of cable of the same gauge as the inside wiring, a GFI receptacle, and a weatherproof cover.

Sorry I forgot to mention that I still have the old screw in fuse box.. does this change anything

No problem.Good time to check that any #14 wire has 15 amp fuses and #12 wire has 20 amp fuses, and use all time delay fuses.