The Reds will be included in that particular procedure after winning 1-0 against Real Sociedad in San Sebastian, a scoreline which confirmed Erik ten Hag's men finished as runners-up in Group E behind the home side.
La Real's reward for staying at the top of the table on goal difference is to go straight into the Round of 16, for which the draw will be held on 24 February 2023.
United, meanwhile, will have to win a two-legged playoff in order to join them, with those additional games being played on 16 and 23 February.