I have asked the same question about four or five hours ago. @Jason Zentz has given me a link. But the tree linked gowns down. It is a little different from mine. I tried many time to solve the proble, But I failed. So I have to post the question again.
Here is my question
I tried MikTex package manager, but there is not forest.sty!!
– Yuming Feng Jan 23 '15 at 00:50forestis definitely available in MiKTeX as its CTAN page shows. Perhaps you have an outdated distribution? – cfr Jan 23 '15 at 23:49