Learn Spanish (Latin America): ¿Dónde puedo firmar?

When you use poder (can / to be able to) to talk about what you can do, the second verb always stays in its infinitive (dictionary) form. So we say puedo firmar (I can sign), not puedo firmo.

The translation says "can I sign", but where is the word for "I"?

In Spanish, the "I" is built right into the verb puedo. Because puedo strictly means "I can", you don't need to add the word yo (I) unless you want to emphasize it.

If the verb is poder, why is it spelled puedo and not "podo"?

Poder is a stem-changing verb. For most subjects (like I, you, he, she, or they), the o in the middle changes to ue. That is why it becomes puedo for "I can".

Why does Dónde have an accent mark over the "o"?

In Spanish, question words like dónde (where), qué (what), and cómo (how) always have an accent mark when they are used to ask a question.