How do I enter RMDs that were not taken for multiple years?

How many years tax returns are you filing?

And why?

How many years 5329s are you filing? And why?

Are you trying to compute the penalty? Or request a waiver of it?

How old is the client?

You don't report the income until it is withdrawn. 

You report the penalty, or ask for its waiver, on Form 5329 for each year a distribution was required.  Form 5329 can be filed as a "stand alone," or attached to Form 1040 if that return is required. 

The first thing you should state when asking for the penalty to be waived is that the distribution has already been done, the request being made as soon as the omission was discovered.  

I believe I have to go back to 2014 which when the first distribution should have been made.  So when I file the taxes for each year.  I have to report access for each year.  For example.  Filing in 2014 I would report it in 2014, then again in 2015, I would report the distribution not taken for 2014 and 2015 and do that for every year that the distributions were not taken.  For example>

2014, RMD not taken in 2014

2015, RMD not taken in 2014 and in 2015 for 2015.  In other words report 2014 and 2015 RMDs not taken in 2014 and in 2015..

2016  RMD not taken in 2014, 2015 and 2016 for 2016.  In other words report 2014, 2015 and 2016 RMDs not taken in 2014, 2015, and 2016.

And do that for each year until they take the money out.  That would account for the money that still has not been taken out for those years plus the current year.

I am going to try and get a waiver but want to have the figures on hand.

I think you are over complicating things a bit with your thought process.