Make sure you're logged into the forum then go to the free adverts page and you'll find a link "Add/Amend A Free Advert", which is bottom right icon above advert list. Click this and you'll get a list of your ads, then follow the ''Edit Ad'' link on the right of your advertisement. At the bottom of the ad, you'll see "Advert Status?" which you set to "Sold/Remove Advert", then preview it and save by hitting the "Yes, all Ok, submit Advert" button.
It can confuse as it doesn't fully delete the advert, in case you ever re-list it, but it will be removed from the search and free ad listing.
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