Hi @Ram Bjiya,
Welcome to the Community!
If you are looking to create an app to work with Jira Cloud, you should take a look at the documentation here:
Specifically this section:
In step 2 it describes how to turn your instance into developer mode to try installing a locally created app.
I hope that helps!
You don't install .jar files on Cloud. You have to create your app, get it marketplace listed (privately if you want), then you'll be able to draw it into your Jira.
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