To do this you have to do a strike without anyone in your fireteam dying. So if anyone dies in your fireteam you can just quit and try again ideally you want to do it with 2 other people that you know. You can ether do this in the vanguard playlist or the strikes themselves I recommend selecting the strikes them selves. A strike looks like this on the map:
The recommended strikes are:
The Devils' Lair (Earth)
The Nexus (Venus)
Dust Palace (Mars)