How can one atone for the sin of falsely accusing a woman of adultery to go along with bad company, knowing that the woman is innocent?

You have committed a grave transgression. Firstly, you have wronged yourself by openly committing a sin and by lying, which is the path to immorality. The Prophet, peace and blessings be upon him, warned those who lie to make people laugh with destruction (Wail), and a servant may utter a word that incurs Allah's wrath, causing him to fall into Hellfire. Secondly, accusing innocent people of indecency is an act of injustice, aggression, and the spread of obscenity. Islam considers it a major sin, and its punishment is the Hadd of Qadhf (slander) which is eighty lashes. The Prophet, peace and blessings be upon him, counted it among the destructive sins. And whoever says about a believer something that is not in him, Allah will make him drink from the pus of the inhabitants of Hell. Therefore, you must engage in sincere repentance, regret what you have done, associate with the righteous, and keep away from bad company. You must also inform everyone you spoke to about this woman that you were lying and that she is innocent of what you said, and advise your companions to repent.