Usually somebody in this situation would go through the whole RCIA process, since they (presumably) did not receive sufficient instruction in the faith earlier-on. At my parish, we also have an ‘abbreviated’ program for people who already had significant formation in the faith but were never Confirmed, which we use on a case by case basis.
It is the pastor’s decision which process is most appropriate in each individual circumstance.
The best way to get started is to make an appointment with the priest at your local parish. He can guide you through and help ensure that you get the appropriate formation before receiving the Sacraments, however much or little you might need, based on your individual needs.
But don’t be surprised if he recommends the full RCIA experience. I’m probably biased since I coordinate the RCIA program for my parish, but I think you’ll get a lot out of it – including, hopefully, some followship with others in a similar situation. It depends on the size of the class, but at my parish we usually have at least a couple people who are ‘returning’ Catholics.
God bless! Best wishes in your journey!