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We recently purchased JIRA Server license. can you please confirm how to use the same?
is this floating kind of license which we install on server then we can use it on client machine or it is only for server?
It's only for the server, you don't need licenses on client machines.
There are instructions here on how to apply it: https://confluence.atlassian.com/adminjiraserver/licensing-your-jira-applications-938847718.html