Learn Italian: La signora ha comprato i sandali e le pantofole, e se li è portati a casa. - The lady bought the sandals and the slippers, and took them home with her.

The verb here is actually portarsi, a reflexive form of portare. In Italian, using the reflexive adds the meaning of taking something 'for oneself' or 'with oneself'. When the third-person reflexive pronoun si is combined with the direct object pronoun li (them), the si changes to se, giving us the combined pronoun se li.

Why is the auxiliary verb è used for taking things instead of ha?

Normally, portare (to take or bring) uses the auxiliary avere. However, because the second half of this sentence uses the reflexive form portarsi (to take with oneself), it must use essere. In Italian, all reflexive verbs require essere as their auxiliary in the passato prossimo.

Why does the past participle portati end in -i if she bought both masculine and feminine items?

The pronoun li replaces both i sandali (masculine plural) and le pantofole (feminine plural). In Italian, when a group of nouns contains mixed genders, the masculine form takes over as the default. Therefore, the combined pronoun is the masculine plural li, and the past participle portati changes its ending to agree with it.