In Inventor, three axes and three planes already exist in each new part. These are called the origin axes and planes. Typically, unless you have changed your application options to "No new sketch", Inventor 2012 opens a new part with a sketch already active on the XY plane. Is this not what you're seeing, or are you asking in advance of actually using Inventor?
I recommend you start here
Are you coming from experience with another program?
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