Go to the My Subscription window. You can access Subscriptions from the switcher.
You can add add-ons by clicking on the Edit/ Buy add-ons from the My Subscriptions screen or go to the Manage Plan screen to do this.
You can find that a wide range of add-ons that are over and above your plan are available. Typically, they have descriptions on their use cases, and are associated with quantity/monetary value if applicable.
Choose the add-ons that you require.
On the right-hand side, you will notice the update in your pricing break-up.
Once done, click on Update Subscription.
Note - If you are an online paying customer (with a saved card on file), you will be charged based on the add-ons you have purchased, immediately.
If you use alternate payment methods (offline paying customer), you may notice limitations in the range of add-ons that you have. Please reach out to firstname.lastname@example.org for support.