Winnetka Heights HOA

I have lived on Hartsdale Dr. for more than 30 years.  Came to this area as a child , but always noticed the difference on our block compared to El Tivoli neighborhood and wondered why our street could not join in the association.  I looked on the city of Dallas website to find my neighborhoods association and it list EL TIVOLI to my suprise.  So is this iformation correct?  There is also a BeverHills Association...  Can anyone give me information on how to start an association if we are out of these limits?