You already have an account where you are enjoying the services you enrolled for when it was set up. Now you wish to add additional services. These may include Skype for Business or other services as they become available.
From your base account you will need to access the account settings. You can check this by clicking the small upwards pointing arrow in the top-right corner of your screen. Access to the account settings is via the small right pointing arrow adjacent to your account name. If you're looking to check the available services of a sub/client account you may need to click on the Account Link indicated.
Once you are at the required account and have accessed the account settings you will see the Edit Available Services link. Click this to expand the section:
The available services are shown with ticks against those that you have already selected.
If the service you wish to use is not shown, you will need to contact your partner to have this added.