The position of the mast is important for weight distribution on the board. At the beginning, you can always set the mast to the "Center" position as shown in the picture.
By moving the mast further back, you require less effort in the front leg. If you move the mast further forward, you need to shift your weight more towards the front. The "right" position needs to be determined individually and should always be adjusted based on skill level, local conditions, and personal comfort.