Gadget export
To export the Twinkle 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:
* Twinkle[ResourceLoader|dependencies=mediawiki.user,mediawiki.util,jquery.ui,moment|rights=autoconfirmed]|morebits.js|morebits.css|Twinkle.js|twinkleprod.js|twinkleimage.js|twinklebatchundelete.js|twinklewarn.js|twinklespeedy.js|friendlyshared.js|twinklediff.js|twinkleunlink.js|friendlytag.js|twinkledeprod.js|friendlywelcome.js|twinklexfd.js|twinklebatchdelete.js|twinklebatchprotect.js|twinkleconfig.js|twinklefluff.js|twinkleprotect.js|twinklearv.js|twinkleblock.js|friendlytalkback.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.