I agree with SmokeyBear
Photobucket is super easy and FREE
Just register and open the "free" account... it gives you enough space to upload over 3,000 photos. Plus, you can edit them, resize them, even send them to a Facebook or Twitter account... all for free!
Once you open the photobucket account and upload some pics, you just hit the "image" icon on the WMAS 'reply' screen and copy / paste the photobucket 'direct link' URL into the URL field on the WMAS image upload screen.
The picture you want pops up in the 'preview' field, then just hit 'OK' to add to your post.
Simple, easy and totally 100% free