我的孩子不清楚英语“in for to of on with"在句子中的用法,

建议买一本语法书，有比这更全的介词用法

in 在什么什么里面
for 为了什么
to 后常接动词 表示要做什么
on 在什么什么表面上
with 表示一种从属关系

so you are after for preposition ? for the sake of your kid...here you are...
PLACE (in, on, under etc )
Your book is on the table.
We waited in the bus.
The cat sat under the tree.
TIME (in, on, at )
I can meet you at 9 o'clock
I can see you on Sunday.
I was born in 1997.
PURPOSE,QUANTITY (for)
He went to the store for foods.
We bought it for ten cents.
PLACE OR DIRECTION (to. with )
The park is next to the school
He went to the store.
He went with his sister yesterday.
I ate it with a tea spoon.
Measure (of)
Please buy me a piece of cake
There's a lot more ...

in 在...里面
for 为了...
to “朝/向...”常跟在不及物动词后面，如go to...
on 在....上
with 和...一起，如 come with me

这些都是常用介词.介词是英语中用法最为复杂的词类之一.在此只能简单地介绍一下.
首先,要记住它们的基本词义,如：
in 在……里,for 为了,to 到、向,of ……的,on 在……上,with 和……一起
其次,介词常用在动词之后,如：
I live with my father and mother.我和我的父母一起生活.
如果没有具体的动词,那就要用在be动词之后,如：
Your book is on the bed.你的书在床上.
再者,要记住介词的一些常用搭配,如：
look for 寻找,in the end 最后,listen to 听……,等等.
以上是有关介词的一点最基本的内容,希望对你辅导孩子能有所帮助.