Without knowing anything about you, it's very hard to say what you need to do with any degree of specificity. I know what I'd do, if you came to me with the request.

Step one would be to sit down for an interview, of sorts, over lunch or dinner. Find out exactly where you left off. Review your logs. Get a feeling for where you are, why you quit, and your approach, attitude, and goals. I'd have you take a sample test, see where your needs lie, and schedule an evaluation flight. I'd start you on some ground training, with the books and materials necessary to start refreshing, and I'd have you take an online CFI refresher course...good way to get introduced to the material quickly, even though you're not actually refreshing an existing CFI.

Once we had a good handle on what you needed specifically to advance, we'd tackle the weak areas, polish the strong areas, and tailor your training to your needs (which chance as you go along, meaning the training should be flexible enough to change with you).

The first step in that training is to get you current and comfortable in the aircraft in the left seat. Then move you to the right seat, and get you talking and flying. Progress from there is entirely up to you, at your pace, as your time, preparedness, aptitude, and finances will allow.