你好！
英语中的do一般可以这么用：
1.构成一般疑问句 Do you have a baseball？
2.do + not 构成否定句 You do not have a baseball.
3.构成否定祈使句 Do not take that thing!
4.放在动词原形前 加强该动词的语气 I do want a baseball.
5.用于倒装句 Only then did we realize the importance of learning English.
6.用作代动词 -Do you have a baseball? -Yes, I do.
英语中的to一般可以这么用（用法太多了 只列常见的）：
1.表示“到......去” 表方向 He went to Canada last year.
2.表示“（时间、程度、结果）到......为止” He worked from morning to night.
3.表示目的 To your health!
4.表示比较 对比 They won the game by 5 to 4.
5.表示（对象关系）属于 对于 She is very kind to me.
那什么时候用啊
用于什么地方
追答具体要看句子