Set up advanced filters on the collection page
4. In the "Filter Type" field select "Side Filter" as advanced filters only work with the "Side Filter"
5. In the "Tags to filter by" field, type in the "FILTERNAME" you used in the product tags. For example if you have tags:
Size_S, Size_M, Size_L
you will type in "Size".
If you have:
Color_Red, Color_Black, Color_Blue
You will type in "Color"
The end result will be: