1) Visit the site and read everything. Figure out what features you want to install. For me, I really needed the CID "fixing" and not the notification. However, just to be safe, I'm installing all of the requirements.
2) Visit the files page, download v0.9 and make sure the pre-requisites (listed on that same page) are installed. If your distro doesn't have the modules ready-made, you'll have to get them from CPAN. However, I don't think that you need to download the pre-requisites for the features that you're not going to use. Note: Nathan has listed the SSLeay module as Cipher::SSLeay. This is an error. The module is currently named Crypt::SSLeay.
3) Enable the CDR feature. My notes for doing so are here. Nathan points back to notes on VoIP-Info.
4) Put the tarball in a working directory and untar it.
5) cd into the resulting directory
6) cd into the AGI folder
7) Edit the files and make the appropriate configuration changes. (Hint: look for the parts (near the top of the script) surrounded by # signs and title "Configuration Options".)
8) Move these files into /usr/share/asterisk/agi-bin (or wherever your version of Asterisk stores its AGI files).
9) cd up one and then into the cgi-bin directory
10) Edit the files and make the appropriate configuration changes.
11) Create a file called "hoodahek" in /var/www/cgi-bin (or wherever your version of Apache stores its CGI files) and move these files there.
If all you're installing is the CID "fixer", your finished. I will add notes about the notifier scripts later.