It depends on the service you want to add to your account.
In most cases you can order a new service via the order from on our website: https://fragnet.net/?page=gameservers

At the checkout, on the bottom there will be the order form, if you are an existing customer, you will be able to log into your member account and therefore the service will be added to your existing client account. 
This will also mean you will have the service added to your Game Panel account.