I don't own the form so cannot make changes to the js or html but would like to automate the fields in the form for the convenience of users of a separate system. Does anyone know how I can create a URL (e.g https://dementiafriends.secure.force.com/ea?FIRST_NAME=test&SECOND_NAME=test ) to automate this referral form?

https://dementiafriends.secure.force.com/ea

I have found other threads but the answers don't seem to work for this form, but I am not very good at looking into the page source to find names/tags etc of the form fields so I am going wrong somewhere.

Any help would be appreciated, many thanks.