I want to use Krita on mac 10.8 but the version available on this site is only for 10.9

please help me !

Unfortunately that won't be possible unless you build it yourself, which in turn is very tricky and not fun for people who don't have experience with building.

We don't have enough money to work on improving Krita for the mac at the moment, including building one that supports older versions. The builds we make right now are a proof of concept.