To find it, you need to consult your owner's manual. This is the most reliable source. The manual will show you the location of the fuse boxes (there's usually one under the hood and one inside the cab, often under the dash) and a fuse diagram that shows which fuse(s) control the power windows.
Without the manual, searching online for a "2002 Ford F-150 fuse box diagram" might yield a diagram, but these diagrams vary slightly depending on trim level and options. Using an incorrect diagram could lead to further electrical problems.
In short: Check your owner's manual first. It's the only way to be certain.