Okay Suzzie,
I'm sorry. I'll start from the beginning with it.
Obviously you'll have your picture pulled up.
Crop it to where you want.
Then go to image then click on Resize/Resample image. (or Ctrl+R)
Then set your new size to Width 150.
(The Preserve Aspect ratio box below the new size box should be clicked.)
Once you type in 150 it should automatically fill in the height so the picture isn't F'd up.
Then you save it the way we discussed before.
That help?