I took out a loan on my 401 k which I pay back with a payroll deduction.

As long as you are paying back the 401k loan, there is nothing to enter about that on your tax return.  If you default and do not pay it back, it will be taxed as a distribution and you will get a 1099R.

If you are paying back the loan as agreed, then this is not taxable income and does not need to be reported on your return.  You should not have received a 1099-R for it. 

If you default, it then becomes taxable income subject to penalty if it is an early withdraw.