Gadget export
To export the calc-core 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:
* calc-core[ResourceLoader|dependencies=ext.gadget.rsw-util,oojs-ui-core,mediawiki.widgets|type=general|hidden]|calc-core.js|calc.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.