Resizeing can be done two different ways. Resizeing is often used in conjunction with cropping. lets start easy and work up
Once the picture is opened go to VIEW>IMAGE INFORMATION.
From here note the size of the image you have up. Avatars need to be 46 pixals by 64 pixals, in case of mega size Avatars they need to be 102 pixals by 116 pixals.
Use the selection tool click on one area of the picture press the left mouse button and drag it down and to the right hand corner.
You should see a broken line around the area that You had selected.
Go to IMAGE>CROP TO SELECTION.
You should now see a piece of the original picture gone and the picture a smaller size.
You will need to go to IMAGE>RESIZE
Type in102 where it says WIDTH
You will need to do this over and over again until such timeas when you type in the 102 that the HEIGHT will equal 116 (this is for the megahead Avatars).
Use the selection tool click on one area of the picture press the left mouse button and drag it down and to the right hand corner.