The default database user has dbo permission, if you want to have different mssql database user with different permissions, you can follow the steps below to create them.
1.Login to your Hosting Control panel
2. Click "DATATBAES" from the top menu, then choose the MSSQL to reach mssql management.
3. Click "Database User Manager"
4. In the pop up window, select the database with you want to create additional database user for, then fill the new database user info, select the corresponding permission to create it
5. Now, you have done, you can use this new db user in your connection string.