When you are at the charging station location, select a charger compatible with your EV (e.g. CCS, CHAdeMo). If you want to double-check it’s the right charge point, the charger ID in the app should match the ID on the physical charging point.
The charger itself may provide specific steps to complete before starting a charge.
Tap the 'start a charge' button and follow the instructions on your phone screen - you can always try again if you tap the wrong charger!