To add your Steam account to your Raptr profile, you would first want to visit: http://raptr.com/account/identities where your identities are added.
Then you would want to add either your Vanity URL or your Profile unique ID.
An example of a Vanity URL:
An Example of a Profile id:
Be sure you're entering the right one, once you have the right one, and provided your profile isn't set to private, we'll pull in the correct data!