You don't have to do anything. When you enter your 1099-G for unemployment, TurboTax will automatically give you the $10,200 exclusion. The exclusion will appear on Schedule 1 line 8.
If you have already filed your tax return without the exclusion, the IRS will recalculate your tax return and send you the additional refund for the $10,200 exclusion. It might take several months to get it. DO NOT file an amended return. For details see the following IRS announcement.
IRS to recalculate taxes on unemployment benefits; refunds to start in May
