try searching the forum for old info
If you search this forum for "posting pictures" you will get your same question on May 26, 2006.
Clem Wixted gave the answer.
Also the answer is in the "Help, Rules, & FAQ" first page about 2 screens down.
If you have trouble with sizing your picture before uploading see the "posting photos!@#$?????" post from Sept 15, 2006 and the good replies with ideas on what to do before you try to post a picture.
good luck.