Go to Items in the main navigation menu.
Press Custom Attributes in the upper right corner.
Press + New Product Attribute.
Under ATTRIBUTE CODE, enter “size”. All letters should be lowercase.
Under ATTRIBUTE NAME, enter “Size”
Under CUSTOM ATTRIBUTE TYPE, select Product attribute / string from the dropdown menu.
Under FRONTEND INPUT TYPE, select Select.
Under SELECT VALUES, press + Add New.
Under VALUE, enter the first size. For example, you can enter "small" but the value must be in lowercase.
Under LABEL, enter the size as you want it displayed to your employees and/or customers. i.e Small.
If you need to add more sizes, enter those values and labels by pressing + Add New for each new size.
Under UI COLUMN SIZE IN POS, enter “4”
Press Save Changes.
Create a Size Attribute
If you want to assign sizes to your products, you'll need to create a size attribute in the backend.