Yes you need to have short term gains from SALES.
If you have a net loss for the year you can only deduct 3,000 (1,500 MFS) max on your tax return. The rest you have to carryover to next year. You have to report the carryover every year until it's used up. You can't skip a year.
See Publication 550. Capital Losses start on page 66
https://www.irs.gov/pub/irs-pdf/p550.pdf
And here's Schedule D
https://www.irs.gov/pub/irs-pdf/f1040sd.pdf
