Learn Dutch: Wij wilden voor onze rechten demonstreren. - We wanted to demonstrate for our rights.

Because wilden acts as a helping verb here. In Dutch, when you have a conjugated verb in the normal second position (like wilden), the main action verb (demonstreren) is pushed to the very end of the clause in its full infinitive form. This follows the exact same word order rule as the laten we structure you're learning in this lesson!

How would I change this sentence to say "Let's demonstrate for our rights" using this lesson's grammar?

You simply replace wij wilden (we wanted) with laten we (let's). Because both structures put the main verb at the end of the sentence, the rest of the words stay in the exact same place: Laten we voor onze rechten demonstreren.

I learned that "right" is a het-word (het recht). Why do we use onze instead of ons here?

You are correct that the singular is het recht, which means "our right" is ons recht. However, the noun in this sentence is plural (rechten). In Dutch, all plural nouns behave like de-words, so you must always use onze with them.

Is wilden a regular past tense verb?