On the left navigation pane, select Billing > Subscriptions.
Select Add subscriptions + on the right side.
Under Other Plans, hover over the ellipse (…) for Power BI Pro and select Buy now
The problem comes in bullet "3", I don't see any "Add subscriptions" button in my screen nor any other option to explore... It's incredible but I want to pay and I just can't find the option! Can anyone help?