The first time a payment comes in, the application does not always know which contract it belongs to (for example when the originator's name does not match the tenant's name). You assign it once, and from then on the application remembers your choice and automatically assigns any similar future payment.
Prerequisite: your bank account must be synchronised with Smovin. Without synchronisation, no payment appears to be assigned.
Steps
On the Dashboard, find the Payments to assign card and click on it.
The Payments to assign page lists every payment you need to assign.
Hover over the row of the payment you want to process: the Assign button appears on the right of the row. Click on it.
In the Assign payment window, check the Originator, the To account and the Value, then open the Select contract drop-down and choose the matching lease contract.
Click Assign to confirm.
The payment is assigned. The next time an identical payment comes in, it will be assigned automatically: the program "remembers" what you taught it.
Special cases
Splitting a payment across several contracts (for example a home + a garage paid in a single transfer): in the Assign payment window, click Add contract to payment. See: How do I assign a payment to two contracts?
Payment unrelated to your rental management: click the three dots … to the right of the row, then Ignore (remove it this time) or Ignore and moved to the blacklist (also automatically ignore all similar future payments). To ignore several at once, tick them and click Ignore. See: What is the blacklist?