Trying to Debug Directly in VStudio

I have to do some work on an existing codebase that has this folder structure:

\root
   ECommerce
      Common
      Images
        sitenameA
      Scripts
      Sites
        sitenameA  <<< This is the startup project >>>
           bin
           Controls
           MasterPages
           obj
      Styles
        sitenameA
   Infrastructure
      Binaries
      General.Client.Common
      General.Common
      General.Server.BusinessLayer
      General.Server.ServiceLayer

The previous developer told me that the only way to debug this application is to:

1. Start a browser.
2. Navigate to the deployed website.
3. In Visual Studio, attach to the browser.
4. Go through the web app and debug.

This is fine when I'm ready to test the deployed version running in IIS but, for starters, I would just like to be able to go through the regular Run-Debug cycle entirely within Visual Studio.  The PROBLEM is that everything in ECommerce, in another area outside of "Sites\sitenameA", isn't referenced within the "sitenameA" project.

I've just never seen a VStudio solution organized this way but understand it makes sense in this case because there's a "sitenameB", "sitenameC", etc.

If you were in my shoes, how would you get it to run in Debug mode in VStudio?

Robert