With the help of the link How Do I Install/Upgrade/Uninstall an AppExchange App, you can easily understand how to install/upgrade/uninstall the app from the AppExchange.
PS: View Mass File Download, Salesforce file download app on Salesforce AppExchange: https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3A00000EcsAOUAZ