It is possible to train yourself for MMA competition, but it requires some level of proficiency in one or more of the components that make-up an MMA Athlete: stand-up, clinch and ground fighting.  For example, you may be a Division 1 Wrestler in college and so you would incorporate some cross-training with strikers to modify your base discipline in order to defend against strikes.
However, if you do not have a base discipline it is a good idea to join an academy that can introduce you to striking, clinch and grappling.  Each dimension comes with its own techniques, principles and theories, so it is helpful to work with an academy that provides a structured learning environment.