Learn Italian: Certamente, puoi entrare adesso. - Certainly, you can enter now.

In Italian, when you use a modal verb like potere (can/to be able to), the main verb that follows it stays in its infinitive (dictionary) form. Since we already conjugated puoi (you can), entrare (to enter) doesn't need to be conjugated.

Which 'you' is puoi referring to?

Puoi is the informal you (tu) form of the irregular verb potere. If you were speaking formally to a stranger or someone of authority, you would use può instead.

Does the ending -mente in certamente mean something specific?

Yes! The -mente ending in Italian works just like the -ly ending in English. It turns an adjective into an adverb. Here, certo (certain/sure) becomes certamente (certainly).

Can I put adesso between the verbs, like in the English 'you can now enter'?

In Italian, the modal verb (puoi) and its infinitive (entrare) usually stick together like glue. It is much more natural to put adverbs of time like adesso at the very beginning or end of the sentence.