Gadget export
To export the ProveIt-classic 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:
* ProveIt-classic [ResourceLoader |type=general |dependencies=jquery.ui, jquery.textSelection, mediawiki.util |actions=edit] |ProveIt-classic.css |ProveIt-classic.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.