Pardon me if I'm wrong but you would like to make your picture bigger in size? Or am I mistaken and misread your post?
Ah, you can re-size it using websites like Photobucket or even here (http://www.resizemypicture.com/).
It shouldn't be too difficult to do. On Photobucket, you'll need an account but on the other website I provided, you don't. Merely follow the instructions provided on the sites and your photo should be bigger in no time at all.
Sloow down and don't stray off-topic.
Adding images is simple, floof.
Adding pictures to your posts.
(http://i55BannedImageSite/wv4bnn.png)
Go to Tinypic.com. This is the home page. You do not need an account, but you can create one if you'd like.
Click 'Browse'. Pick the photo you want and click it. You can choose what size you want it as well.
(http://i53BannedImageSite/15gt8v7.jpg)
Type in what is says to in the box. Easy as pie. Then hit Upload Now.
(http://i54BannedImageSite/33tm0cg.jpg)
The codes are located in the light yellow rectangles. Copy the code under 'IMG Code for Forums & Message Boards'. Paste the code in your post.
(http://i51BannedImageSite/2z56bsi.jpg)
Wala. Picture (c) Tigg and Delay.