15% off to entire collection showing price comparison

[Meaghanmariee]

Hello hello, 

I am looking to apply the 15% off discount on all Lighting (the whole collection), but it seems as though the only way to do this is one by one and im having to do the math myself. There must be an easier way!? I specifically want to be able to see the price comparison on the entire collection. My store is Beaupresley.ca

Please help! thank you 🙂