You do not need Family Tree Maker, though you may wish to at some point. There are advantages to having a stand alone program.
There are very good tutorials available on Ancestry. Recommend you read and research a bit before diving in.
Take a look at the "First Steps" here http://www.ancestry.com/cs/Satellite?childpagename=USLearnin...
By all means use others trees as a guide, but it is not good practice to just copy trees without verifying the sources. Do the research, follow the documentation and look at the sources. That way you'll catch errors before they get in your tree.
Welcome to a fun and rewarding hobby.