How do i sell adspace on my website?

[Patrick]

I have a pretty large website, think it's the 11,000 biggest in the UK, which isn't brilliant, but i'd say fairly impressive, currently were making a profit but no revenue(give largely to charity) , it's a forum website, we have people who know about web admin, but nobody that knows about adspace, and banner advertising, If we could get advertising it would greatly increase out profit in some respects I imagine. In simpleton terms, i'd like to know how to sell adspace to companies, and the kind of profit i'd possibly expect, whether it's worth the hassle etc

thanks
It's a football supporters website/forum, i know who the target audience is, and what companies to probably approach, but not how to create the banners manually or how adsales works