You'll need to get an external host that allows you to show images on different servers (generally referred to as "hot-linking"). You cannot post images directly from your hard drive, or attach them to our forum.
2 good options are:
Photobucket or
Geocities
Note: To use geocities you'll need to save your images from .jpg to .txt then post.
Once you have your host you will use the IMG tags inside the post to show where the image should be displayed.
Example: [img]Http://img.photobucket.com/album/v9999/artistname/folder/imagename.jpg[/img]
If you need help with vB Code, please read the
vB code list
Please see jetpack42's comprehensive guide
How to post a picture on the forum for detailed information.