As far as I know, the Adobe store will not allow you to add a program and "create" the bundle... you will need to cancel what you have for a refund and buy new
What MAY help...
Select a topic, then click I STILL NEED HELP to start Premiere Elements Online chat
Or go back to the store page to find a cancel/refund link
Did you purchase Premiere Elements 13 from Adobe Direct? If so, are you within 30 days of that purchase? If the answer to both of those questions is Yes and it appears to be, then you should explore
Contact Adobe Chat clicking on the following link
Membership, Account, Payment
Payments, Invoices, Orders
If the link does not hold its set, then you will need to navigate to the Chat Panel using the above titles as guides.
Under the conditions mentioned at the beginning of this reply, I am speculating that Adobe should be able to give you your money back for the Premiere Elements 13, allowing you to purchase Photoshop Elements and Premiere Elements which are sold together, but are still really standalone products. How Adobe opts to do that is at its discretion.