Now I get it that you want to set this web application as your default application.
Why havent you tried out what Chris Mathews has explained
here very clearly. The same steps have to be followed whether it is a 6.1 application or a 7.0 application.
I have verified this too.
However here is a slight correction
Open up the WebLogic console. Select your server, click on the Connections tab. Then select the HTTP tab, select your default web application from the drop-down of Default Web Application. Restart the server. Done.
Please Note the name that is in the popup will be the name of the directory where you have unzipped the web application you have specified.