A. Unfortunately, if you originally installed the SCSM 2010 RTM media and then upgraded to SP1, you can't later install the SP1 SCSM self-service portal on the existing box. If you just have SCSM 2010 RTM, you can install the self-service portal on top of it, but once SP1 has been applied, you can no longer add the portal component.
The solution is to install the SCSM self-service portal on a separate server that has IIS installed. You need the IIS role with IIS 6 metabase compatibility, ASP.NET 2.0, Basic and Windows authentication, and the .NET Framework 3.5.1 feature enabled on the box. You also need the authorization hotfix installed (KB 975332).
You can now launch the SCSM 2010 SP1 setup.exe and select to install the web portal component. You need to specify the Service Manager SQL database instance and database name along with an account to use for connectivity, which will be the service manager services domain account you specified during the Service Manager management server installation. This account must be a member of the local admin group on the SQL Server hosting the Service Manager database and be a member of the sysadmin database role on the SQL Server.
The best practice architecture is to separate the self-service portal service on a different server from the management server, so this isn't actually a bad workaround to not being able to install the portal onto the management server.