Here is how you can add variants:
Step 1: Click on 'Menu' on upper left corner
Step 2: Click on 'Inventory Management'
Step 3: Choose the item to which you want to add variant
Step 4: Click on 'Add Variant (or) Unit' at the bottom right corner of the screen
Step 5: Fill in the required details and
Step 6: Click on 'Add'
Step 7: Click on 'Save'
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