I went to turn the water on in the back and it will not turn. How do I unlosen it? Thanks

If this is a metallic spigot just shut off your main water and use an adjustable wrench to losen the cap on the shaft below the handle. You could completely disassemble it and clean out all the crud but loosening the cap should let you open the valve. Open and close several times, turn the main back on.

If this is a metalic spigot just shut off your main water and use an adjustable wrench to losen the cap on the shaft below the handle. You could completely disassemble it and clean out all the crud but loosening the cap should let you open the valve. Open and close several times, turn the main back on.
Just wanted to let you know that this worked and I could turn with the handle after turning as you stated. Thank You