You want to know HOW to post an ad, then check out the Self Help Center.  It is located on the upper right of the Newbie Board, and has tons of good information for both hobbyists and Providers.  I have included a link to the Ad Posting Guidelines for you.  I don't know where you are located, but you can find and post on the Regional Ad board for the area closest to where you are doing business.  Just follow the guidelines.  You can only post an AD every 7 days.  Also, if you already have any reviews posted, that means you have a review profile.  This profile will contain information about the services you provide as well as contact info and links to your web site and/or Ads from another site.  You may want to contact support about linking that profile to your user account.  That way when you post on any TER board, a link to your reviews will show up under your user name, which will allow people to find out more about you.  Hope this helps, and best of luck!