You don't need really to unstring it. But if you feel you must, remove the pads on the D bar (assuming it's an Excal) BEFORE you do to avoid ruining them.
Best way to unsting a recurve is with a STRINGER. Slip it over the ends and **** the bow with the stringer. Remove the string, then let the stringer down with your ****er (or by hand if able to). The Excal web site has a tutorial on same.