Learn Farsi: امشب به پارک می‌رویم.

It follows the rule for the present indicative tense: the continuous prefix می‌ (mi-) + the present stem رو (rav) + the 'we' ending ـیم (-im).

Where does the present stem رو (rav) come from?

It comes from the infinitive verb رفتن (raftan - to go). While past stems are regular and easy to find, present stems in Farsi are often irregular and just need to be memorized. For رفتن, the present stem is رو (rav).

Where is the Farsi word for 'we' (ما) in this sentence?

You don't need to use it! Farsi allows you to drop the subject pronoun because the verb ending ـیم (-im) already makes it perfectly clear that 'we' are doing the action. You would only add ما at the beginning if you wanted to emphasize that we are going, as opposed to someone else.

Can the present tense verb می‌رویم be used for future actions like going later tonight?

Yes. In Farsi, the present indicative tense is very commonly used to talk about planned actions in the near future. It translates smoothly to 'we are going' or 'we will go' in this context.