I'm self-employed. My mileage is partially reimbursed by an agency. How can I use TT Home & Business to deduct the diff between my .47 cpm and the standard mileage rate?

I am self-employed, contracted through an agency that reimburses my mileage at .47 per mile.  How can I use turbotax home & business to deduct the difference between the standard mileage rate of 53.5 cents per mile and the amount I have been reimbursed?  That amount was not included on my 1099.  I have seen this question answered for employees, but not for how to enter this into turbotax home & business for self-employed users.  Thanks!