Visit this page in your account:
Select "Reload your balance".
A modal will pop up:
Enter the balance you would like to add.
Speak will use your attached credit card to deduct the defined balance.
Automatically, your balance will update in the account.
You will be able to use that balance to transcribe and analyze your media files.
Don't have a credit card added?
On the same page, Select "Add a Card", fill out the details and hit "Add".