There are several home-computer genealogy programs that offer free versions. Search for genealogy program free on the web.
You can download a GEDCOM file of your tree to your home computer, then import the same file to the genealogy program to view it. The file itself will not be changed, but you should save the genealogy-program's file after importing. Each genealogy program is a little different. Within each, you can also have the program generate a GEDCOM file incorporating any changes you have made, and open that with any other genealogy program.
These will not end up helping you with a numbering system **in the Ancestry.com Member Tree.** The home genealogy programs all have a few choices for how to number the people in your tree, depending on what kind of report you want the program to generate -- from the program, not in or from your Ancestry.com tree (which can not generate any reports unless you want to create a book via Ancestry.com's "My Canvas" setup).
So try out at least one genealogy program, see what works best for you.
There is an Ancestry/Rootsweb message board for Genealogy Software within "Topics", with much discussion regarding currently supported programs -- which include TheMasterGenealogist, RootsMagic and FamilyTreeMaker -- and there are others. The message board does not have a subtopic for all of the presently-supported programs, but if you browse around a little there you can at least get a sense some of what's current and some persistent issues/problems with some.
http://boards.ancestry.com/topics.software/mb.ashxDo not get discouraged. Every one of us has had a lot to learn, and even the most skilled can always learn something new. High quality genealogical work can not be done as a quick project!
Take advantage of the resources in the Ancestry.com Learning Center, read genealogical blogs, and never be afraid or embarrassed to ask questions.