Auto populate Fields

Auto populate Fields

Greetings,
I created a module called "Attivazioni4P", in this module I added a lookup search field to get data from another module, "Companies" (default zoho "accounts" module).
I would like to automatically populate the fields in the new form by simply searching the lookup.
I know this type of question has been asked many times, but I can't get this feature to work. By default on other CRMs.

Please give me a hand?
Thanks