Learn Hardcore Portuguese (Brazil): Confirmo o agendamento prévio, a senha e o atendimento presencial. - I confirm the advance appointment, service number, and in-person service.

Breakdown of Confirmo o agendamento prévio, a senha e o atendimento presencial.

What form is confirmo?

Confirmo is the 1st person singular present indicative of confirmar. In plain English, it means I confirm.

So the speaker is the person doing the confirming. This is a complete verb form by itself; Portuguese does not need a separate subject pronoun here.

Why isn’t eu included before confirmo?

Because Portuguese often drops subject pronouns when the verb ending already makes the subject clear.

The ending -o in confirmo tells you it is I.
So both of these are possible:

Adding eu usually gives emphasis, contrast, or extra clarity.

Does confirmar need a preposition here?

No. Confirmar is normally used as a direct transitive verb, so it can take a direct object with no preposition.

That is why Confirmo o agendamento... is correct.
You can think of it as to confirm something = confirmar algo.

A different structure is also possible with a clause, for example: Confirmo que recebi o e-mail.