"Are we able to go?" / "Can we go?" are just in regular present tense - "Können wir gehen?"
But "Könnten wir gehen?" is conditional - "Could we go?" / "Would we be able to go?"
Past tense is "Konnten wir gehen?" - "Could we go?" / "Were we able to go?"
Conditional past tense is "Hätten wir gehen können?" - Could we have gone?" / "Would we have been able to go?"
well ,in DW online courses I've learn that "koennen" means "can" it's in the present , "konnten" is "could" it's in the past, then "koennten" also means "could" and it's used When asking polite questions, making requests (favors, advice), expressing wishes or setting conditions like in a resturant "koennten sie mir bitte die Speisekarte bringen?"="could you please bring me the menu?" guys,please correct me if am wrong
Read some of the other comments and the links in them.
Könnten is a form of the subjunctive mood, and indicates something that might be possible.
Konnten is simply past tense.
Können is simply present tense.
So, your sentence means "Can we go?". Anyway, this exercise involves translating German to English, so the German phrase is set.