How can I edit the Materials, Shipping & Returns, and Dimensions tabs in my new shop?

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I have recently setup up a shop on shopify using Down and I have many items in my shop.I have added my descriptions etc.but there are tabs thatunderneath that say,Materials,Shipping & Returns,dimensions and cear intstructions.I can not see anywhere how I can edit these?at the momentthey show nothingand I,m stuck.Can anybody help with this please?