You manually enter them into your tax return. Then you either efile your tax return to the IRS and state or you can print and mail the tax returns. If you mail them in yourself you have to attach all W2s and any 1099s that show withholding on them.
How to Efile
https://ttlc.intuit.com/community/e-file/help/how-do-i-e-file-my-personal-individual-tax-return/00/2...
