To add an event or product to a subscription click the Packages tab at the top of your admin area, select Subscriptions, then edit the subscription. In the subscription editor click Add Item to add a new ticket type or Add Product to add a new product. Select the event and ticket type, or product from the dropdown and update the subscription.

The new items will now be listed with a checkbox for Add To Existing Subscribers. Select the checkboxes for the new items you want to give to existing bundle holders, and click the "Email Selected New Tickets and Products to Subscribers" button. This will add the items to the customers existing transactions and QR codes, as well as send subscribers an email notifying them about the new items.