When renting with Open, you don't meet the owner directly: the keys will be inside the car directly. The owner usually leaves them in the glovebox, in the sun visor or in the storage area between the two front seats.
If the car keys aren't there, check out the car manual that the owner wrote, it will tell you where the owner left the keys. You can find it on your Drivy app as soon as your rental has started, on the rental page.
If the owner didn't specify where the keys would be, or they're not where the owner said they would be, try contacting the owner for more information.