<a rel="nofollow" target="_blank" href="
https://www.irs.gov/pub/irs-pdf/f1099msc.pdf">https://www.irs.gov/pub/irs-pdf/f1099msc.pdf</a> Box 3 is for 'Other Income', which would normally go on Line 21 of your Form 1040, and be taxed directly from that entry at your regular marginal rate.
