What is the correct present-tense form of poder in Spanish?

The form depends on the subject.

I am able - yo puedo

You are able - tú puedes

He/She/It/You (formal) is/are able - él/ella/usted puede

We are able - nosotros/nosotras podemos

You (plural) are able - vosotros/vosotras podéis (vosotros / vosotras is an archaic form of you in plural) - ustedes pueden

They are able - Ellos pueden