After you have successfully signed up, activated your account, and verified your credit card on our platform, you will be able to access the management portal for Europe and US, your e-mail address and password to log in.
Once logged in, go to the billing icon 
Now click on ‘Buy Credits’ and choose the amount:
Click on ‘Pay €xxx’. The credits will appear on your account now and be charged from your Credit Card.
Please note that adding credits to a customer account, can only be done to the administrator(s) of that account. Not by the user(s). Read here how to switch your users to administrators and vice-versa.