Pre populate a form field value

I am new to mautic and want to know how to pre populate a form field ?? I have read mautic documentation on forms but I am not able to understand form there how to do it…

Thanks in advance for help.

I am new to mautic and want to know how to pre populate a form field ?? I have read mautic documentation on forms but I am not able to understand form there how to do it…
Thanks in advance for help.