how do i use the import/image board option on aku shaper?

hi, i am trying to make a surfboard template. i wanted to copy a board so i saved a photo of the board i wanted to make then went to image bord>outline>then downloaded the board to the background. te only problem was first that the board in the background came out huge! and i have no clue how to scale it. also if anybody has rocker templates that are medium,low to medium,or continious could you give me the measurements?