When you already did something with B2B11g, then you probably already know how to connect to the B2B UI, and have found out that it's not available by default.
By default the B2B UI is not targetted to a managed server. It can be done very easy in the weblogic console (http://adminserver-host:port/console). Go to Deployments and look for b2bui, when found click on it.
Then in the next screen click yes: