If a customer has not scanned his app while at the store, and you want to add a visit to his counter:
You first go to "Customers"
Then you look up the customer via their e-mail or phone number:
On the bottom right (below Timeline Activity) there is an option to "Manually add Visit/Payment" (the first option)
Once you open it a sub-menu will open up, allowing you to enter the details:
Location of visit (which branch)
Purchase Identifier (usually a receipt number)
Time of Visit (date)
Press on Add Visit, and then refresh, and it will show you the customer's visit.