I have make a really simple progression of chords (F-C-G-Am) and I want to add like an "introduction" with notes

The thing is that I dont know really much of theory music so I dont know what scaleis property to play

Any ideas?

Thanks! And sorry about my English, hope you guys understand me
If you're playing in the key of C (which the progression is in), the notes you should play are: C D E F G A B. If it were me, I would play F E D C B A G, the descending scale starting on F. It's fairly simple, but it works. For something more complex, you could take the notes of the chords you use: F A C C E G G B D A C E. This is a more complex and harmonically interesting pattern.