-Download Zathras 2.8
-If you already have an older version of Zathras
--Rename or backup your existing Zathras directory then extract the archive in your TBP directroy it will create a new Zathras directory.
-If you are installing for the first time
--Just extract in your TBP directory.
-Grab the appropriate 3.7.0 builds and updated launcher from the release thread
-Run the launcher and select Zathras as the active mod.
That's all there is to it.
Note: There were no changes between 2.7c and 2.8 so if you already have 2.7c you do not need to get this version.