IRA contributions are not reported on a W-2. W-2 box 12 contributions are employer plans such as 401(K) plans, that are NOT IRA's. If on your W-2 then do not enter it ANYWHERE else.
A 401(K), 403(B), and certain other employee sponsored plans that might be on your W-2, are completely different accounts from IRAs. IRAs are controlled by different sections of the tax code and have some very different rules for contributions and withdrawals, and should never be confused with each other. A 401(k) is NOT an IRA.