Add colours and sizes for your products under “Add/Edit Attributes”. Note that the same product attributes you have added appears each time you add a new product, so that you do not have to reenter it again, unless you have new product attributes to add.
After adding attributes, select it and click save at the bottom of the page. To select multiple attributes at one go, press 'ctrl' button on your keyboard and select the attributes at the same time.
You can also arrange the order of your product attributes by dragging the icon.
OPTIONAL: “Set Size Pricing/Stock”
This is for merchants to set size pricing or stocks for their products. Simply set a new price or stock amount for the different sizes, and click save and enable it.
This is how it looks like when your customer clicks to view the product. Notice that the price changes accordingly to the size if you have edited the size pricing.
Next, upload and sort your Product Images.