skywalkerjedi

Note that many Immigrant Visas are suspended until the end of 2020 because the April 22 proclamation was extended: https://www.federalregister.gov/documents/2020/04/27/2020-09068/suspension-of-entry-of-immigrants-who-present-a-risk-to-the-united-states-labor-market-during-the
Extended by June proclamation's Section 1: https://www.federalregister.gov/documents/2020/06/25/2020-13888/suspension-of-entry-of-immigrants-and-nonimmigrants-who-present-a-risk-to-the-united-states-labor

Start here https://travel.state.gov/content/travel/en/us-visas/immigrate/the-immigrant-visa-process/step-1-submit-a-petition/step-2-begin-nvc-processing.html and follow through the subsequent pages, it is pretty much a step-by-step of the process including listing all the civil documents you need. 
But yes short version is you don’t submit documents etc until the case reaches the “current for filing” date. Still a few years away, see table B of the visa bulletin.
 

No problem at all. Just write a letter and explain why they not filed income tax.

I had my interview last Sept 16, and a week after, I got my Oath schedule for Oct.