It is quite simple (if you run the 0505 image of android). Just open SuperSU app and let it work its charm (installing dependencies). Do a reboot, and go get a root checker app from the store to check if it is all ok.
This worked for me
FYI, I used the PhoenixCard image of android 5.1.1 build 20160505 on my Pine A64+ 2Gb
This worked for me
FYI, I used the PhoenixCard image of android 5.1.1 build 20160505 on my Pine A64+ 2Gb