This can be done in any command line interface on the server like the terminal in Web Host Manager.
Imunify 360
First, unregister your existing license key:
imunify360-agent unregister
After that, for key-based licenses, run:
imunify360-agent register (Your Key)
For IP-based licenses:
imunify360-agent register IPL
Use the word IPL, not an actual IP address for this command.
Imunify+
CloudLinux key-based license:
imunify-antivirus register (Your Key)
CPanel IP-based license:
Upgrade free imunify+: imunify-antivirus register IPL
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Once any of these are active, run this and add the Imunify tools to each cPanel account.
/usr/share/av-userside-plugin.sh