The external hdd is probably usb, its just a case of plugging that in and transfering everything like pics, files, movies etc over to that via drag and drop.

Why have you bought another internal hdd ????, i ask this as your going to transfer all your stuff to the external hdd which thus frees up all the space on the one thats full, why dont you fit the newer bigger drive as your 2nd drive for storage only and keep the drive you currently have for your os.

If you want to only have the one internal drive ie the newer bigger drive then youll need to freshly install your choice of windows onto it.

Dave.