You must be the administrator of your JIRA instance in order to install the Gadget House for Jira app.
Gadget House for Jira is available for JIRA Cloud and Jira Server
Installing Gadget House
Log into your Jira instance as an admin user.
Click the Settings drop-down menu and choose Apps.
Add and manage Jira Marketplace apps.Locate Smart Dashboard for Jira
Click Try it Free then Start free trial to download and install your app.
You're all set!
Click in Manage Apps on the left-hand sidebar menu to manage your apps.