The app plans charging against the prices you pay. Entering your tariff correctly makes sure the car charges in your cheapest hours.
Your energy supplier's time blocks are already set in the app, for example a normal rate and an off-peak rate. Fill in what you pay per block. You find these prices in your energy contract or in your supplier's app.
The chart under the prices shows how the day is divided. Check it against your contract.
If you pay the same price all day, switch on the single-rate option and enter that one price. The chart becomes flat, because there are no cheaper hours to move charging into.
With one price all day, solar charging can still help: the car charges on your own solar power when an inverter is connected. See How Solar Charging Works.
Update the prices in the app when your contract changes. The app uses them for planning and for the savings it shows.