Unzip "Fritz_ET_Final" and place the folder "fritzbot" in your C:\Program Files\Wolfenstein - Enemy Territory folder.
Unzip "Fritz_final_patch" and place its contents in the "fritzbot" folder.
You'll also need "Fritz1_1.00.pk3" which has all the latest map waypoints and updates. This file should be placed in the "fritzbot" folder as well. It can be downloaded from
http://forums.bots-united.com/showthread.php?t=6006
That ought to do it!