Hi AlwaysPacing
When you complete an online application you come to a page where it asks if you want to include any supporting evidence, if you click yes you then have to click on where the file is held on your computer, it will then upload the document.
You can upload numerous documents but they have to be in a certain file format.
You can send any documents to HMCTS in a paper format, make sure you put your reference number on each page, I would also include my name and National Insurance number just to cover myself and send it by recorded delivery, I would advise you not to send any original documents, send copies of the documents, just in case they go missing.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems