This tutorial series may help:
https://www.youtube.com/watch?v=i6SUqg1N2_s&index=1&list=PL5BaCj8qGxsD1qcTLKU7YVUtKgV9jZenZ
You could also take a look at this forum post:
https://forums.unrealengine.com/showthread.php?89892-AimOffset-and-Turn-in-Place-Animation-Replication
Click link under “Long version” skip to about 4:00mins into the video and you’ll see one method of creating a blendspace using the Rifle Animset Pro along with how to implement it.