If you paid by credit card, it is instantaneous in the vast majority of cases, and your candidate area will automatically display when a payment is recorded.
If you paid by SOFORT transfer, the payment validation is automatic and can take up to 5 days. You do not need to do anything once you have made the transfer. It will be validated automatically in the following days, with the payment date being the date of your transfer, not the date of receipt.
If you paid using cryptocurrency such as Bitcoin, it is usually just a matter of a few minutes before you receive payment confirmation, but sometimes it may take longer depending on whether the network is congested or not. In any case, you can also see on your side when the payment is still pending validation by the blockchain. Several confirmations from the Bitcoin network are always required for your payment to be validated.