The first leg of the Round of 16 tie takes place at the Wanda Metropolitano Stadium.
"Some of our players will not be received with a red carpet," said Rangnick.
"Mentally, we need to be prepared for an emotional and hostile atmosphere. This is not the easiest of draws."
"We have the chance to reach the quarter-finals," added the German. "We have to show we're up for it.
"If we get through, it will raise the levels of confidence. In the Champions League, you need to perform on the highest possible level. We have to be prepared for the challenge and be mentally strong.
"It is about getting the best possible result. The fixture won't be decided on Wednesday, it will be decided in the second leg.
"We want to play in the Champions League and show everybody we are able to beat this team. If we win the Champions League, we qualify next season.
"First we need to play two good games against Atletico to try to progress to the next round."
Manchester United have not won the Champions League since defeating Chelsea on penalties in the 2008 final. Since then they have lost two finals in 2009 and 2011, both to Barcelona.
