It seems odd that you'd put in the time, money and effort needed for a 'professional' film with no idea what to do when you're done. In any case, one route would be through the festival circuit, where several successful films have found distributors. Your film needs exposure now, and you won't get it unless you explore every avenue.
And you will need a distributor: no significant theater or group will take on your film without one. An agent can help you get to distributors. It isn't unusual for a professionally produced film to spend almost as much on promotion and distribution as on initial production. If you can't afford it, you have to make a deal with someone who can.
At the very least you'll need to create a DCP (digital cinema package) and DVD screener copies for any festivals or agents you contact. Check the web sites of the major and minor festivals to see their submission requirements. Good luck.