Refer to the instructions https://www.irs.gov/pub/irs-pdf/i8949.pdf

Find the proper code from above, then refer to https://accountants.intuit.com/support/en-us/help-article/form-1099-b/generating-form-8949-column-f-... for how to do the input. 

@George4Tacks’s posting is good and comprehensive, covering all types of adjustments to basis including that of your issue. My posting below details steps in Lacerte to address adjustment pertaining to your specific question.

Go to Screen 17 Dispositions

On the left column under the heading Sections, click Schedule D

On the third row Adjustment to basis if reported incorrectly on Form 1099-B, box 1e, enter a positive number to increase the reported basis, or a negative number to decrease the reported basis.