There is no official version of the Meteor Client that supports Minecraft 1.8.9. Meteor Client is built exclusively for the mod loader and focuses on modern Minecraft versions, typically ranging from 1.14.4 up to the latest releases like 1.21.x.
If you specifically need a client that runs natively on 1.8.9 for PvP or performance, official and widely recognized options include: meteor client 189 download verified
Once you have the verified .jar file, installation is straightforward: There is no official version of the Meteor