F3 on string 6 is actually F1, so one half step above a standard tuned basses lowest note, F3 on string 5 is actually F2, so a half step above a standard tuned guitar's lowest note, the rest is an octave lower. this site has the octave numbers wrong. E2 is the lowest note on a guitar, A2 is what the A string on a standard tuned guitar is.
Anyways, first tune to D standard (DGCFAD) which is what this tuning is based off of. then drop the 5th string from G to F, and the 6th string from D to a super low F (a half step above a basses E string). for this tuning i use d'addario .11-.56 medium top heavy bottom set, the same strings i use for D standard, drop C, AGCFAD, A#FCFAD, and GGCFAD. if you wanted to keep a guitar set up in this tuning you could put a heavier string on the bottom. i just hit the note softly.
Please use the below form to submit a song for FFCFAD that is not already on gtdb.org.