I purchased the service manual for my 2019 from Nissan Publications. It came on DVD. You should be able to purchase the manual for you 2020 the same way.
Thing is they stopped selling whole manual as such and now selling subscription to view it, by days/month/years, and overly expensive IMO. Still looking.
I subscribe to alldatadiy for my vehicles just google it... It's reasonably priced and blows away many of the 'repair manuals'.. Although I do also have the books as they are more helpful on the side of the road..