When you walk with a knee scooter, you need to ensure that you rest your knee on the seat with your back upright. This will prevent you from leaning back onto your leg which can be painful if you have an injury, while it also leads to instability.
Move slowly! Knee scooters are meant to move slowly so you don’t want to try to move too fast as that can cause you to fall. You want to keep both hands on the handlebars. With the foot that’s on the ground you want to slowly push yourself forward.
When turning, such as into a room, make sure that you take a slightly wider turn so that you have enough space in which to turn without twisting your hands, which can cause you to fall.