Include whole posts on another site?

I’m new to wordpress and I have been searching for the php code to include the posts onto another webpage. I have used fanupdate in the past and on the admin of that there is the code you can copy and put on your website and everytime you post it updates and posts on the other site.
I know it should be <php include… but it’s not working. I was looking for an explanation for this but I can’t find one. Someone please help?