Step one, lose weight, get in shape.
Dancing is easier if you are light on your feet. Trust me, you will feel better about yourself, sweat less, increase your life expectance and last for hours on the dance floor if you spend half an hour or so a day jogging. Oh, and here is another reason, fit people eat more than fat people of the same weight--so if you love good food, get fit.
Step two, take a lesson and practice.
Learning a dance is like learning a forign language, take a class for goodness sake. As a added befefit the instructors are often hotties.
Step three, enjoy yourself.
Practice at home until you can dance without steping on each others feet then go for it. Dance with someone you love, it is a great part of a romantic evening.