When first installing them you may want to use the "buddy system".
I install the top half first. Just like standard plastic handguards, I put the front in first and then push the back end down (while pulling the delta ring back). I usually will just try to get one little corner in past the delta ring (that would then hold the delta ring back), then I can regrip the delta ring and pull it further back.
The handguard tools do help out quite a bit. I am sorry but we are totally sold out of them right now.
hope this helps. . .