My Passport - How do I change from category lists to file lists? Do I delete all and start over?

I have only had MyPassport 3 months.  When I began to use the external drive, I did not see a place to copy by category or by file.  Thus it copied everything by category and now I do not know how to locate which files are on the external drive.

In the instruction manual it said I could change to file instead of category but I wouldn’t be able to do something(?) after I did that.  I truly do not understand what the manual is saying about getting my information transferred to the external drive by files and not categories.  Right now I am unable to find out what files are on the external drive.

I thought I might have to delete (clean off the external drive) everything and start over, but I’m not sure about that.  As you can tell this is my first external drive and I’m not too sure how to work with it.

My second item is do I need to leave the external drive plugged into the computer all the time or can I remove it and when I put it back in it will copy any new material?? 

Thank you for all your help.  I truly appreciate any help I can get at this time.

How did you copied the files?