Navigate to where you had previously unpacked the plugin. Normally, it's under /usr/src/varnish.unixy.net.
1) Run the uninstaller
[root@varnish varnish.unixy.net]# pwd
/usr/src/varnish.unixy.net-1.0b
[root@varnish varnish.unixy.net]# python uninstallvarnish
#note that uninstalling the plugin will remove the plugin's currently-saved settings. All rules will have to be readded post update.
2) Login to your client area via this link: http://www.unixy.net/secure/clientarea.php
3) Select My Products & Services from the top menu
4) Click on the View Details button next to the licensed product
5) Scroll down to the Downloads section at the bottom to download the new script
6) Upload the script to the /usr/src/ and follow the rest of the installation instructions here or refer to the original installation instructions sent when you first purchased the license:
https://www.unixy.net/secure/knowledgebase.php?action=displayarticle&id=4
7) Once the plugin is installed, you can access the functions via WHM via https://VALID_IP:2087 where VALID_IP is the licensed IP, which is visible in your client area by selecting the plugin service.