That's one way to do it. But someone brand-new to the forum can get confused with manually editing BBcodes. If OP registers and makes an account on Imgur, the site will provide him with a simple way to resize the images he has uploaded with a click of a button. It's not always perfect, but it has helped me many times. After selecting the size he wants, all he has to do is click on the copy button above and paste the results into the forum.