How do I mark my Want request as received?

Go to the Your Posts page and click on the Want post that you want to mark as received. Click the button or link labelled "Mark as Received" that is below the post title and fill out and submit the form. This will remove your old Want post from the group listings.

If you're using the website (and not one of the apps) and if you requested multiple items in one Want post and only one or two of the items have been received, you should instead go to the New Post page and submit a Received post that only lists the items that were received in the item description and details fields.