Did you take any money out of the 401(k)? If not, you don't get a 1099-R and you don't enter anything in your tax return. If you did take money out, you should have gotten a 1099-R. If you didn't get it, call the plan administrator and ask for another copy.
Any money that you put into the 401(k) will be shown in box 12 of your W-2 with code D. That's the only entry you have to make in your tax return.
You don't enter anything in your tax return for just having a 401(k), if there was no activity in the account. You only have to enter anything if you put money into the 401(k) or took money out.
