Gadget export
To export the URLShortener-sidebar gadget, click on "Download" button, save the downloaded file, go to Special:Import on the destination wiki and upload it. Then add the following to MediaWiki:Gadgets-definition page:
* URLShortener-sidebar[ResourceLoader|dependencies=mediawiki.util,oojs-ui-windows,mediawiki.widgets,mediawiki.ForeignApi|default|type=general|skins=minerva]|URLShortener-sidebar.js|URLShortener-sidebar.css
You must have appropriate permissions on the destination wiki (including the right to edit system messages) and import from file uploads must be enabled.