-Or- Provide a SteamID or Steam CommunityID or Profile URL
Help! What are these things?
A SteamID is a unique number associated with every steam account. You can find yours by looking in the URL of your profile if you don't have a vanity URL (see Steam Community ID below), or you can use a site like Steam ID Finder. The ID we are looking to is often referred to as a SteamID64:
Steam Community ID
A Community ID is a unique vanity url ID associated with your account. Take my GabeN's account for example: http://steamcommunity.com/id/gabelogannewell. He has set up a unique ID of "gabelogannewell" that refers to his account. To set a community ID for yourself go to edit profile and then set a unique community ID.
To get a profile URL, just visit a steam profile on the web, copy the web address (URL), and paste it into the bar above!