How to connect a mybb login script……

[Fait]

I have a question I want to make a unique webmaster Site that should be a big hit with my unique ideas now im going to add a video section & A Social Networking section for webmasters (like facebook but unique) how do I get A Mybb login to be used on my Webmaster Social Networking & Video Site (like if you are a member on the forums you can submit and take part in the social networking & Video Section with your forums account) And when they submit a video or status comment and will display there signup username what they used on the forums

How can I do this with Mybb I know http://taste.com.au did it with phpbb and added extra features for there users
Like Google & you tube uses the same accounts for sign in
Thanks In Advance
Spudster