In order to obtain this trophy, you need at least 6 enemies within reach.
During the tutorial, you learned how to do more than 1 CQC on multiple enemies (Press R1 after your first takedown). You need to do this 6 times. At face value this looks challenging, however it really isn't.
Once you get done with Chapter 1, you will unlock the "Recuit" option on the Mother Base screen. Go there, and you will have to perform CQC on every soldier in order to convince them to join you. I believe there are 7 or 8 soldiers here, so just perform CQC on the first, then hit R1 for the rest. Trophy will pop shortly after the sixth guy goes down.
Questions, corrections and neg vote justifications below.