I just put the round bale out in the lot in a round bale horse feeder cut the strings off and let them have at it. One 1400lb round bale feeds my 4 horses about 10 days.
You can just cut the strings and peel off layers as needed. If you do that put a tarp over it to keep the weather off if it.
Depending on how old the bale is the first few inches of the out side will be weathered but edible. The bottom is usually nasty, I dump it in my manure pile once the bale is down to nothing
Edit: if you are putting the bale someplace that you want grass to grow later on put it on some old tire, a pallet or anything that will keep it up off the ground. If you set it right on a grass area, you will end up with a bare spot in the grass. We buy all our bales in the summer and store them all winter so we put them all on pallets to keep the bottoms from going too bad.