Did you make note of how to play the E Minor chord in a cuatro? If you have, then the F Minor chord will seem awfully familiar to you.
Both chords have the same figure, the only difference being that the F Minor chord consist of a bar as it is the E Minor chord moved down by one fret.
Take a look at the comparison of the two:
As you can see, they both have the same figures. The marking of the frets does need to be adjusted since the bar comes into play. The marking should be using the index finger to mark a bar on the 1st fret of all of the strings followed by:
The notes that compose a F minor chord are C, F, G#.
Take a look at how this chord is played using a Cuatro in the video below: