Edit default fields through custom app

How can we edit default fields through custom app so that whenever that app is installed in a new site, those changes are reflected there.

You might want to write a patch

https://frappe.github.io/frappe/user/en/guides/deployment/migrations

https://discuss.erpnext.com/t/use-property-setter-to-override-doctype-name/4990/2

Property Setter or Patches what is better for the above?

@royprotim,

Depending on your requirement, Patch will be executed only once, Property Setter, on the other hand, will sync after every migrate.