1. To Start with, you need a program designed for the job, such as FSScreen.
This is a small, yet very useful utility for taking screenshots in FS98/FS2000/FS2002 without having to pause the flight sim, so that you can paste into MSPaint. Developed by Matthias Holzer, this tool stores your screenshot everytime you hit the "Print Screen" key and stores that screenshot in your FSSCREEN folder and it can store up to 1,000 screenshots, while you never have to stop or pause your flight sim!
2. Read the Instructions On Use/Installation.
3. Fire Up FS, and shoot 'em shots.
4. Get A photobucket account, only photobucket does the job the best, so therefore only photobucket will be mentioned.