I don't know what you mean by the first sentence but to answer questions on Brainly you just click on the question you want to answer and press "add answer"
2. You answer brainly questions by clicking add answer and then you will see a green "add your answer" button on the top of your screen and you click that to submit you answer.
Explanation:
1. I think that is what you meant for the first question you asked.
2. I literally just answered this question so I think I know how to answer questions.