First open an account with any of these Aftermarket domain dealers- Afternic, Dan ,Sedo, Squadhelp, etc. List your domain names, verify ownership on their sites by pointing the Nameservers from your Registrar to the Aftermarket merchant you are listing the names on. You can either put the price as Buy It Now (BIN) or as Make Offer. Then you can promote your names by out bounding to potential endusers.