N5
にする
To decide on, To choose, To make something into, To view something as
今日はここまでにする。
Let's stop here for today.
Explanation
「〜にする」 means you decide on one of the choices: used when ordering, shopping or fixing a date: 「コーヒーにします」 (I'll have coffee), 「会議は明日にする」 (We'll hold the meeting tomorrow). To ask: 「何にしますか」, 「どれにしますか」 (What will you have? Which one?).
Mixed up with
「〜にする」 is your own decision; 「〜になる」 is something that comes about naturally or ends up as: 「Aにする」 = 'I decide on A', 「Aになる」 = 'it becomes A'.
When ordering, 「コーヒーにします」 is the proper form; 「コーヒーになります」 is common in part-time-job speech, but literally means 'it turns into coffee' and is considered imprecise.