Go to the customer by clicking on All Customers from MSPControl home page, then choose your customer from list.
From customer's home page click Create Hosting Space button, select your pre-configured hosting plan, type customer's domain name and click Create Space.
You will see Creating hosting space window. Hosted organization will be created during this process as well.
Space Statistics page will appear when done. Depending on hosting plan quotas you either ready to give it away for customer or have to add some hosting add-ons to allow resources.