Go to form "Other Income Statement - Schedule 1, Line 8"... scroll down to line 24, Other Taxable Income, and enter "UCE" (Unemployment Compensation Exclusion) in the description field.  Next, enter the amount of the excludable portion of the UC as a negative amount (e.g. -$2,000).

Go to Schedule 1 to review your input and you should have an offsetting credit against the taxable UC.