In addition, cut four pieces at 530mm, these are your braces for your main supports. From the ground edge measure up 1100mm, this is the centre mark for the centre main support brace. From the top measure down 300mm, this the centre mark for your top main support brace.
Lastly cut your timber slats for the roof of the storage unit. You'll need 51 pieces at 800mm long to make your roof area complete.