bbpress submite button

Hi

I am trying to make the submit button bigger and centered on my bbpress install. At the moment it is stupidly small, can you help. I have enabled support login if needed. You can see the button below. It would be good if looked like my other buttons on the site, the ones done in VC.

http://ohbother.forumite.co.uk/forums/topic/portal-on-shield-k1/

Thanks