First you need to get them hosted somewhere on the Internet.
You could do it here using our vB Image Host feature. It's up there in the menu between FAQ and Community.
Click that and you'll get a drop down box. Select Upload an image and you'll get a page with a bunch of slots to upload a picture.
Click browse and navigate to your picture on your computer.
Once you've got them all set in the slots, Click Upload.
Make sure your pics are the right size or you'll get an error. The upload page shows you the sizes.
Things will spin for a bit and then you'll be taken to your images. You might see an error message at the top before you get sent to the images page. Just ignore it.
Then when you have your images, you'll see some code underneath each one.
You want to highlight the code labelled BB Code and copy and paste that in to your post - it's easiest to have your post open in another window or tab in your browser.
If you host them somewhere else and they allow linkiing, just get the URL of the image and paste it into your post, then put a [img] before the url and a [/img] after the url.
So, it would look something like this in your post before you submit it.
[img]http://www.moparnuts.com/forums/imagehosting/331440df2c2d3452.bmp[/img]
but after you click on submit (or preview) it will show the actual picture like this: