First a shout out to ModernHam [KN4MKB] on Youtube
for "How to use Wires-X on the FT3D and C4FM (System Fusion)". I had watched a number of the "Hamtubers :-)" videos since these are overwhelmingly returned when doing a Google search for this stuff. Most of these videos were useless for understanding how the radio works as they almost all seem to be produced within minuutes of the radio becoming available and even when supposedly showing how to do something like connecting the FT3D to a YSF room tend to just gloss over details (like did you just press the Back key? or the Disp key or X key)? KN4MKB was on point and very clear in his Youtube video which was very refreshing. So, the instructions shown here are largely because of his very clear and on topic explanations. Worth the subscription to KN4MKB's channel!
BTW I haven't seen these instructions on how to connect YSF, FCS and XLX from the FT3D radio written up anywhere else so if you find this useful, have corrections or something you would like me to add, then please let me know (I'm on QRZ).