I have a 93 Bronco Full Size, and it won't start.

Check your new alternator. Probably bad right out of the box. Happens a lot.

The battery has discharged, and or the connections are at fault. the battery can self discharge if it has a defect. then check the alt light when it runs again before condemning anything. inspect any fuses and cable connections.

Thank you for your input. I also got the suggestions to take a wire brush to battery connectors. Even if there is no corrosion I guess here in Oregon they get rusty through the rainy season. That ended up working I couldn't see any rust but it worked!! Thanks again for your input.

The corrosion battle is not about rust or visible "cheese". it is about the gases from a battery, the "sweating" at the posts and the presence of oxygen in a wet environment. any looseness, darkened surfaces can cause resistance you may not see, but could measure with a DVOM. Normal maintenance would include noco pads and posts and clamps brushed clean to a shine. for longevity, apply battery connection sealer, after they are right. There are brushes available for about $4.00 that make it easy. calvan or kd tools at a store selling american made ones are worth your time and money

The ones I get are in a red and white package, they are at tool town or other specialist of that type. also on a tool truck that services technicians needs. hard to find at other stores because they mark them up out of price range. Then they discontinue them.