I've used this plugin on a server instance of jira, but I'm working in a new company where they use the cloud version of JIRA, so I need to know how to installed this plugin on JIRA cloud.
Unfortunately the plugin you specified only works and supported on JIRA Server and not on JIRA Cloud as per https://marketplace.atlassian.com/plugins/com.rozdoum.jira.jiraFreshbooksPlugin/versions
Marlon, in addition to Chander's answer we have a policy for restricted functions in Cloud as you can see here:
I hope this helps.
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