Mega backdoor Roth contribution and older traditional IRA

Hello,

 

we are married filing jointly, and have filed taxes already for 2019. However, I realized I had a small contribution made to a Roth IRA (Roth 401(k)) via my employer using the mega backdoor. I did not file the 1099-R and need to file an amendment now. Now, I had opened a traditional IRA for my wife(who does not work) in 2015 and made a contribution back then, in her name. We do not have any other IRAs, only 401(k) accounts and some money in pension from previous and current employer. So couple questions:

- how do I file an amendment , what is the best process? I filed thru TT Premier on Mac

- what is the impact of the above existing traditional IRA situation, and how should I deal with it during the filing of amendment.

 

Thank you for the advise!