Gadget export
To export the SettingsUI 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:
* SettingsUI[ResourceLoader|dependencies=jquery.ui,mediawiki.user,ext.gadget.libJQuery|hidden]|SettingsUI.js
You must have appropriate permissions on the destination wiki (including the right to edit system messages) and import from file uploads must be enabled.