Brand new to Dolphin and I need help

I'm brand new to Dolphin and am having a hard time finding reliable information on how to set up my site. I think I've figured out that to take payments via Authorize.net I need to purchase a module but I can't determine which is the best. Same goes for Video. I want to be able to add video to my site and think I need to purchase a module but again can't figure out which is best. Are there any tutorials or good sources for adding modules? Thanks!

You should check here for documentation: http://www.boonex.com/help

It would also help to search the forums, where chances are, all of your questions have already been answered twice.  Videos are a built-in feature, and the module can be installed from Administration -> Tools -> Modules, along with other built-in features, including photos, blogs, and forums.