The plan administrator for your old employer's 401(k) plan is required to send you a Form 1099-R reporting this distribution that you rolled over. They have until the end of January to make this form available to you, so wait for it. Once you receive it, you must enter it under Wages & Income -> Retirement Plans and Social Security -> IRA, 401(k) Pension Plan Withdrawals (1099-R) and answer the follow-up questions to indicate that you rolled this money over to another 401(k) plan.
