If you are lacking First Communion and/or Confirmation, then RCIA would likely be the place for you. The classes are GREAT and often questions will come up that you never would have thought of. Seek the direction of your parish priest, and welcome (back) home!
On another note, I would like to add to the comment suggesting you stay off of these forums. I believe the author has the best intentions and doesn’t want you to be given inaccurate information, and it is true that this forum is open. Especially when you are forming your faith, it is incredibly important that you seek information from reliable sources. I spent two years trying to learn about the Catholic Church, and these forums taught me a lot and brought up a lot of questions. They were a great tool of evangelization and apologetics in my early faith formation, and continue to be so today. HOWEVER, I would suggest that you take what you read with a grain of salt and seek the guidance of a priest, your sponsor, etc. No one human can know absolutely everything, so it is possibly that any singular individual posting on a forum or even conversing outside a parish after Mass could give you wrong information. This is why we have the Holy Mother Church and her guidance.
In your early formation, or if you simply feel more comfortable with these options, I highly suggest listening to Catholic Answers Live and reading the articles posted by apologists at Catholic Answers. You can subscribe to the podcasts and listen at your own convenience, and of course articles are available at any time. In my experience they are strongly in line with church teaching.