Learn Italian: Oggi ho portato un lucchetto nuovo da casa. - Today I brought a new padlock from home.

When talking about your own home or going to or from home in a general sense, Italian drops the definite article. Just like in English you say "from home" rather than "from the home", Italian uses the simple preposition da to make da casa. You would only use dalla casa if you were specifying a particular house, like dalla casa di Marco (from Marco's house).

Why is nuovo placed after lucchetto rather than before it?

Adjective placement can change the meaning of certain words in Italian. Placing nuovo after the noun (un lucchetto nuovo) emphasizes that the padlock is physically brand new. If you put it before the noun (un nuovo lucchetto), it usually means "another" or "a newly acquired" padlock, which might actually be old and used.

Why does portare use avere as its helping verb here?

Portare (to bring or to carry) is a transitive verb, meaning it acts directly on an object. Because you are bringing something specific—in this case, un lucchetto (a padlock)—the verb takes a direct object. In Italian, all verbs that take a direct object use avere for past tense forms like the passato prossimo.