Read more tab, on P2 front page.

I am looking at the P2 theme for a project I am doing. I want the front page to show the latest posts.

I want only to show the first couple of lines of the posts on the front page, with the read more Tab linking to the full posts.

As I only want the authors to write from the front page, and not the back end, I need to code in some way that the posts automatically show the read more tag after a certain amount of words.

Any help would be great thanks

[No bumping, thank you.]