Is there another place that I can enter the deposit I made into my retirement account?

If I understand your situation, you don't record the after-tax deposit on your tax return, but you note the presence of after tax deposits (called "basis") when you receive the distributions from the retirement account.

 

When you enter the 1099-R for the distributions from this account, TurboTax will ask you if you had made any after tax deposits.

 

Here is an example of the screen from the desktop product:

 

 

Note that it asks for this late in the 1099-R interview, so have patience. Also note that the screen in the Online product product probably looks different, so be flexible.

Is this a defined pension?  As opposed to a 401k, 403b, or other plan?

 

There's no tax deduction for buying extra pension credits.  The pension plan is supposed to keep track of this for you, and indicate on your 1099-R statement that part of the pension is non-taxable.  

 

Buying pension credits is not the same as contributing to a IRA, and should not be listed on your tax return. 

Since you mention a pension, presumably this has nothing to do with an IRA.  The only place in TurboTax to potentially enter this would be in the Retirement Savings Contributions Credit section of TurboTax, if it would result in an increase in this credit.