Go to the Filters tab and press the green plus button.
Enter the filters title, e.g. Size. Next, choose the Tags attribute, which will be used for filtering.
Next, you need to add tags for your filter. Click the green plus button.
Add tags associated with the sizes.
Please don’t forget to click the ADD VALUES button after you choose values on one page.
All tags can be edited after you add them.
Next, go to the Filters main tab, click Edit Filters, and find a filter that is called Size. Change Appearance type of the filter to the Size value.
Now, you have the sizes filter on the search results page.