Help Topic: Steam Sidebar
If the administrator has created a custom profile field to retrieve users SteamID, then please input the SteamID as either numeric format or name format.
Visit Steam Profile and check the url to see what the SteamID corresponds. It can either be
/id/XXXXXX/ or /profiles/XXXXXXXXXXXXXXXXX were X is name or number.
If there isn't a custom profile field for SteamID then the administrator wants members to log in through Steam (once). If the member is already a registered member, then he/she can connect their Steam account to the website via UCP. Otherwise when registering just login via Steam.
Steam Sidebar will automatically be added to authenticated Steam Users.
Make sure your Steam Profile Status is set to Public.