integrate forum with site (newbie)

I  have read and re-read the documentation and the past posts... and i am now totally confused! 

I have managed to get the forum up and running, now I would like to place it "inside" an existing webpage.
The site  is designed with CSS and i have a <div> location to place it in.   

My question is/are: What exactly do i put in the webpage <div> section. Do i copy sections out of the forums' index.php file?  Or do i simply refer to the index page in the <div> section.... or should i be editing the template parts  and try to integrate it with this method?   

Thanks for any help.  If this is explained somewhere please point me in the right direction.  I looked at the info in the FAQ section but it really did not clear anything up.   

luvdsun