A customer asked if I would like to go out for a drink, then asked if i was single, doe she want a date?

Alright, Im probably being a little thick headed, but here goes, a lady Ive known casually for a few years came into the store and asked if I drank (this question came after a few minutes of chit chat), I replied yes on occasion, then out of no where she asked if I was single, and I replied yes. Thats basically how the story ends. I want to ask her out but Im afraid to say anything to a woman other than business related when Im working. Is she wanting me to ask her out and how do I go about it? Come on ladies help me with some advice.