copying the field from a different form

copying the field from a different form

Hi all,
I somehow have troubles with finding the answer to this simple question.

I have two forms:
-Companies
-People

Form Companies has 3 fields:
-company name
-telephone
-address

Form People has 4 fields:
-first name
-last name
-company name (a lookup field)
-telephone (I want the field to be automatically filled)

How to set the field “telephone” so it automatically copies data from the field in form Companies ?