Well, you don't have to make an official announcement if you don't want to. It's nobody's business but you're own, really. Dry-humping is NOT mandatory. ;)
However, if you want people to know because you're excited and whatever else, just hold hands. Announce it on your journals. Whatever! It doesn't have to be a spectacle, but you can still show you're proud and excited without being disgusting or superior about it.