Help with twitter updates

the founder member of my group set up a twitter account to automatically update from the news thread in the forum. So every new topic in the news thread automatically went staight on the twitter page

However I have no access to this twitter account, and so cannot add any different updates.

I have set up a new twitter account and would like to change it so the updates from the news thread automatically go to my twitter account and not the founders old twitter account...any ideas how to change it?

Thanks (hope all this makes sense lol)