What type of money market account is it? A money market mutual fund? A bank account? If it's a brokerage account, what is the underlying investment?
A withdrawal from a money market account is usually not a taxable event, and does not have to be reported on your tax return. The withdrawal does not normally produce any taxable income. In the event that it is taxable, you will receive a Form 1099-B from the financial institution at the end of the year. You enter the information from the 1099-B in TurboTax in the Investment Income section, under "Stocks, Mutual Funds, Bonds, Other." You can ask the financial institution where you have the account whether they will be reporting any taxable income for the withdrawal.