It should have printed with your return if you print out a pdf copy of the return. You can also just print out a copy from the link below and fill it out. Form 8453 is basically just a cover sheet.
<a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/f8453.pdf">https://www.irs.gov/pub/irs-pdf/f8453.pdf</a>
