When do u put in t the vinegar when washing black clothes?

i heard if u do that it last longer or something but when do u put it in do u do it in the beginning with the detergent or what some one explain





because i just finished redying a pants with the rit thingWhen do u put in t the vinegar when washing black clothes?
Put it in in the beginning, right with the detergent, if you are adding detergent.

oil