Generally you will want to keep an records related to the distributions and any repayments you have made.
Did you receive an RMD from an IRA in 2020? Did you return some or all of it within 60 days of each RMD distribution? For money that you returned after 60 days, was any of that money returned prior to August 31, 2020?
Generally, you will report the entire distribution amount from box 1 of the 1099-R on line 4a of your Form 1040. Any repayments that qualify for the exception (were made within 60 days of the distribution or before 8/31/20) should be listed on line 4b of your Form 1040. You should also write "ROLLOVER" in the space next to line 4b.
I'm not sure, but you may receive a Form 5498 in May showing the repayments as a rollover, which is how they are being treated by the IRS.
"At times the world can seem an unfriendly and sinister place, but believe us when we say there is much more good in it than bad. All you have to do is look hard enough, and what might seem to be a series of unfortunate events, may in fact be the first steps of a journey." Violet Baudelaire.