Do not tame inside of spike fences or you will lose your precious tame and your life, as I found out. Simply place some carrots in the last item of your hot bar, feed it one and hop on right after. Have fun traveling where it wants.
If it won’t allow you to feed it, knock it out and let it wake up then try again. Most likely due to the fact someone else tried to tame it before. Also, it tells you when to feed it at the bottom corner of your screen. PLEASE UP THIS