Qlik provides instructions on installing extension objects. The instructions can be found on the Importing Extensions page of the Qlik Sense help

Note: We have been notified by Qlik that Sense 2.1 presents an error when uploading certain extension objects. As of Oct. 6, 2015, the QlikMaps extension has been updated to avoid this error. If you are experiencing issues, re-download the QlikMaps extension to and install.