woocommerce; not possible to have site-wide sale?

hi there,
not sure if I can ask this on a WordPress forum but here goes ??

I am running Woocommerce on wordpress, and have started a web shop.

I want to do a site-wide sale, but can’t find any setting to do so.

I can see how to do a coupon, but then the new price will not apply until after they add the coupon at checkout.
I am hoping for a way to apply a discount % to all products, so it shows up on all product pages.

Would appreciate any help ??

thanks
Marie