Contents:

The battery is in the trunk under the compartment cover.
When replacing the battery, disconnect the negative (-) cable (1) and remove the positive (+) battery fuse box (2).
Remove the battery mounting bracket (3).
WARNING - Touching metal surfaces in the trunk under the compartment cover

Do not touch metal surfaces in the trunk under the compartment cover while the engine is operating or hot. Doing so could result in serious personal injury. Turn the engine off and wait until it cools down or wear gloves to replace the battery from the luggage room.
Your vehicle has a maintenance-free, calcium-based battery.
When recharging the battery, observe the following precautions:
Reset items
Items should be reset after the battery has been discharged or the battery has been disconnected.
Kia Stinger (CK) 2018-2023 Owner's Manual: Folding the rear seat
The rear seatbacks may be folded to facilitate carrying long items or to increase the luggage capacity of the vehicle. WARNING The purpose of the fold-down rear seatbacks is to allow you to carry longer objects that could not otherwise be accommodated. Never allow passengers to sit on top of the folded down seatback while the car is moving as this is not a proper seating position and no seat belts are available for use.Kia Stinger (CK) 2018-2023 Owner's Manual: Good driving practices
Never move the shift lever from P (Park) or N (Neutral) to any other position with the accelerator pedal depressed. Never move the shift lever into P (Park) when the vehicle is in motion. Be sure the vehicle is completely stopped before you attempt to shift into R (Reverse) or D (Drive). Do not move the shift lever to N (Neutral) when driving.