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