They work great. How you work it depends on the call - it should have come with directions.
Basically what I do is try to mimic a mad squirrel. Ever walk thru the woods and have a squirrel run out on a limb and "bark" at you? That's the noise I mimic, along with the scream they make. When one squirrel barks the others typically join in and you can then locate them.
Is it a barker of a distressed young squirrel call. I have used both types, but the best is one called Mr.Squirrel call. It is a small metal disk with a hole in the middle that you suck air through and it makes the high pitched call of a wounded baby squirrel....All squirrels nearby will at least come out of hiding to see what is going on. That gives the RT a clear target.
Eagles may soar, but weasels don't get sucked into jet engines "Give a man a fish, and you'll feed him for a day; give him a religion................ and he'll starve to death while praying for a fish."