After the database is setup, the database account used by Clearspace to access the database only needs to have insert, update, delete, and read access to the database used by the application. The only reason that account would need to have any permission to create tables would be if you were having the web setup utility create the database tables but it doesn't sound like you are going to be doing that.
The scripts for creating the database are located in "database" directory of the distribution. Check out the database setup documentation for more information on setting up the database located at http://www.jivesoftware.com/builds/docs/clearspace/latest/ClearspaceInstallGuide.html#ClearspaceInstallGuide-DatabaseSetup
As for creating the database account and granting the appropriate permissions, you will want to reference the documentation for SQL Server for that.