you have to file using the tax software from those years and the associated W-2s. Check with Intuit to see if those packages are still available. An alternate is to go to www.irs.gov and then to forms and instructions, and search for 1040 forms from the associated years.
If all you have is w-2 income, then it is very straightforward to file. Potential good news is that if you don't own taxes, then there will be no penalty or interest, and you will get any refund due (but with no interest), and you no longer have to worry about being caught by the IRS. Potential bad news is that if you do own the IRS then there will be associated penalty and interest on the amount you own, but it will only get worse the longer you wait, so do it as quickly as possible.
