Sorry, it does not work with the Zimbra Desktop version. The zimlet has a JSP part and for some reason the Zimbra Destop does not include some JSP Tag Libraries that are needed in the zimlets JSP. Neither it has the tools to configure the zimlets config. So you need a full zimbra installation. It works with the Open Source Edition as well as with Network Edition.
Basically it's been installed like any other zimlet. See also adminstation guide chapter 13.1 .
CLI example for a Linux server:
1) copy ch_bnc_asterisk.zip to /opt/zimbra/zimlets
2) Install as user "zimbra"
scp ch_bnc_asterisk.zip zimbra@zdev:zimlets/
3) Get configuration template and edit configuration to your needs.
zmzimletctl install zimlets/ch_bnc_asterisk.zip
4) Configure zimlet
zmzimletctl getConfigTemplate zimlets/ch_bnc_asterisk.zip > /tmp/ch_bnc_asterisk_config.xml
5) restart mailboxd
zmzimletctl configure /tmp/ch_bnc_asterisk_config.xml
This is the only part that is not usual for installing a zimlet. This is because a zmzimletctl install does not load the needed jar file included in the zimlet.
Note: The dial-on click regexp is currently made for european style. So its expected that a phone number starts with 0 or +. So american style phone numbers like 1-1234-56789 are currently not catched. Try +1123456789 instead. If you are familiar with regexp you can change it in ch_bnc_asterisk.xml zimlet descriptor file.