And in case you don't know how or where to locate the SQL functionality you would either need to be logged in as the Host (Superuser) or have access to the SQL database that is behind your DNN site. If you login as the Host user you will see the Host menu, then click the Advanced tab and then SQL option.

Please note that executing SQL commands against your database cannot be "undone" or "rolled back" so you should have a good understanding or knowledge of exactly what you are executing. It may be best to try this out in a test environment first.