phphh and wordpress in category

Hi there

I had installed wp united and it worked very well but the phpbb forum are on my main site (on www.******.dk)

I use Gamepress theme

I want it to be in like www.*****.dk/category/forum

How do i do that ?

I just think i kindda make a new site (category) and include the link to my forum or how ?

Im kindda noob to this because im new at this, but my forum site and my wordpress site works very well and i just need the last to make it perfect.

Best Regards

David