@Memc wrote:
I need to combine the additional storage account with the original account. How do I do this?
You can't. There's no way to merge accounts. Your best option is to use a shared folder between the two account to move files from your original account into the upgraded account, then use the new account going forward.
If needed, you can swap the email addresses between the two accounts using a third email address as a place holder, or delete the original account after you've moved your files and that will free up the email address to use on the upgraded account.