1. After you open the .zip, and have opened the FS directory in explorer.
2. Start to click on folders tillyou find one that has a plane discription ( ie: Airwolf v3.1 ) that has a model, sound, panel, texture folder and an aircraft.cfg etc. in it.
3. Copy or paste this folder into your FS aircraft folder.
4. Look for a folder called guages in the .zip and copy or paste it into FS guage folder.
Ps. Sometimes a model maker will not make a folder named and ready for you to drag to the FS aircraft folder. In this case, you have to create and name one yourself. Then move the files in the zip to that folder.
Hope this helps