Rolling - Rolling on a skateboard is what they were made for. Learning how to do it down, up, over and off things is easy with the right stance.
Stepping on and off, pushing with you foot, proper stance.
Once on the skateboard stand knees bent in a slight crouch with your feet and body sort of perpendicular to the length of the deck. This is the best stance to adjust your weight and balance while rolling on the skateboard. The reason for this is that you create four points of balance. Each one is based in one of the four quadrants of the skateboard. This allows you to adjust your balance from side to side and front to back. The crouching allows you to absorb shock and lowers your center of gravity. Both help you remain more stable. It may feel weird at first to be facing sideways.
We walk from front to back all our lives. Going sideways will take practice to get right. Try and find a comfortable stance that lets you get sideways but also feel your balance alright. This is a skill that takes a while to master so have fun with it and try different places to put those feet. Soon it will become second nature.
When rolling try to lift your feet and make tiny steps on the board. Making these adjustments will get you used to the board and how it reacts. The next thing to learn is turning by leaning.