Unzip the autotest-build.zip file to somewhere. Say C:\Program Files\autotest\.
Edit the file autotest.bat as follows
Change the line that reads
set install=C:\home\java-projects\autotest2\autotest-dist\autotest.jar
So that it reads
set install=C:\Program Files\autotest\autotest.jar
Or whatever the full path of the .jar file is.
Edit your PATH variable (use the System widget on the control panel) to include any directories that your test files might need autotest might need (e.g. the directory with the C: compiler).
I strongly recommend testing that all the commands you need autotest to execute from the command line before trying them with autotest.
Double click on a ".at2" file in the tests directory and
associate the .at2 file extension with the autotest.bat file.
Create a shortcut to autotest.bat and
then drag it to the start menu.