Visit the gov.uk site and complete the online form.
It is useful to have an email address that is regularly checked, as this is the quickest way for the Council to contact you.
Supporting documentation can be electronically attached by uploading from the computer on which you fill out the online form.
If possible, take photos of the required documents and transfer them to the computer you use for the form (email or plug in).
If you have a printer that can also scan, this is a good way to capture the documents.