Installation
Log into your Jira instance as a Jira Administrator.
Click the Apps dropdown and choose Find new apps.
The Find new apps screen loads.
Search for Simple Issue Links and click on the app tile.
The App Details screen loads.
Click Get app to start installing your app.
You're all set!
Click Close in the Installed and ready to go dialog.
You can also install the app from the Atlassian Marketplace.