To export the deletion 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:
* deletion[ResourceLoader|type=general|rights=delete|default|dependencies=ext.gadget.libOOUIDialog]|deletion.js|deletion.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.