Nova already recommended the way I did my troll horns. I highly recommend following this
A note about their attachment method, I had a hard time using the snaps. I had to cut a couple wefts in my wig in order for them to properly work, and even then one horn kept popping off. However my friend used the same method and had no problem.
You may want to check out the horns tag
on Homestuckcosplayhelp. They have a bunch of recommendations for attachment and how to make horns!