Quite simply, you open the app and you will see an overview of available tables in your area. If there is nothing available at that time, you can enter a search query yourself. Once you have done that, you can drink a drink in the cafe, as soon as a table becomes available you will receive a push notification of this. Open the app, claim the table and walk to the restaurant. The restaurant does not have to confirm anything itself, once you have claimed the table is for you.