Welcome to Just Answer. I am here to help you resolve your tax and finance concerns. Please feel free to ask anytime you need extra help.
You should begin by determining when was the last time you filed a return.Then sort your records by year so the tax returns can be prepared.The IRS can go back 7 years. You, on the other hand, will be obligated for any tax due during those same 7 years but will only be eligible to receive refunds for the most recent 3 years.
Software is available to prepare the back returns from companies such as TurboTax and Tax Act. The software from each offers a Q&A approach which makes some returns quite simple. You will not be able to file electronically.