If your attribute already exists, then it will be visible as an option in the Step 1: Select Attributes page.
Tick the box next to the attribute(s) you want to add to the product and click Next.
***
Note: If the attribute you want doesn’t exist, then it’s possible to add a new one here. To do this, click the Create New Attribute button.
In the Label field, enter the name of the set of options e.g. ‘Size’, ‘Color’, ‘Style’, etc.
Now you need to add choices to your attribute.
To do this, click the Add Option button within the grey Manage Options box.
Click Save Attribute to save your attribute and add it to the list.