Just under your inbox, you should have a files section. You can upload it there or upload it on the web somewhere and link it from there using the "insert picture from web" button when making a post. If you upload it to the JWD file section then you click on the "paper clip" button when making a post.
Hope this isn't to confusing of an explanation. Maybe somebody else could state it better.
I am not sure if these options work if your not using IE. Everybody that is using a different browser (like FireFox) has problems with formatting issues and such whith JWD, as it is optimized to run on IE. I am not sure if this is one of the problems associated with alternate browsers or not though.