Remind them of the success of the 2018 blue wave.
Remind them of the success of electing Joe Biden.
What really needs to be focused on is how the galvanization of large, urban areas helped bring back key states like Wisconsin, Michigan, Pennsylvania, Arizona, and Georgia. Many, many people voted for the first time in their lives in 2020, and it resulted in the flipping of these states. We need to chip away at the remaining apathetic voters and to show them the direct evidence of people getting out and voting so that these states never flip back, ever.
Additionally, Democrats need to find a way to connect with suburban and rural areas in states where ground can be made up (North Carolina, Ohio, Texas, Florida). They need to gain a better understanding of why these voters wanted four more years of Trump & Conservatism, and to see how they can appeal to these voters. Everything else (Oklahoma, West Virgina, Kentucky, etc.) are most likely just a lost cause at this point.
Edit: Not so fun fact. Not a single county (not even OKC's) in Oklahoma nor West Virginia voted for Joe Biden.