Importing existing applications

I am evaluating the purchase of OS and have a few questions on importing our existing application.  We have a traditional html, CSS, javascript portal site we have been developing on.  I love the features of OS but unfortunately i am not starting from scratch and I want to leverage the work we have already done.  How do I take our existing application and import it into the OS framework.  I would at least like to have the basic layout and javascript tools available for me.  Your assistance is greatly appreciated. 

Additionally there has been alot of work done on themes out there.  How would we be able to import a them built for Dreamweaver into the OS framework so we can start adding cool features to a pre-designed UI.

Thanks for your help.  I am excited to get out team using this awesome tool.
Hi Rob,

You can import only CSS/JS files in order to have the basic layout and javascript.

Regarding the portal logic, you can put it directly in extensions (Using Integration Studio) and then it will be available in the Service Center.

Can you describe the portal a bit more?