Does you mister resemble one that looks like these?
https://www.amazon.com/Houseables-Co...%2C136&sr=8-10
IF so then to open you must forcefully unscrew them to the left. I had the same problem when I got mine. They wouldn't budge and I thought if I applied any more pressure I would break it. However, when I finally applied more pressure turning it to the left, it finally opened. It doesn't have a normal screw type mechanism and you will also find that when you close it after taking it off, you have to be sure it is locked in place or it will fall off.