The installation of Pocket Desk from the Apple App Store is straightforward. The app is free and you just install it as any other app.

However, Pocket Desk requires that a server-side plugin called Pocket Desk Connector is installed on your JIRA with JIRA Service Desk. Pocket Desk Connector adds vital functionality to JIRA that allows Pocket Desk to function. 

If unsure, please ask your JIRA administrator if Pocket Desk Connector add-on is installed on your JIRA. More information is provided in the Administrator's Guide.