Is it religiously permissible to train administrative staff in a company that produces and sells tobacco on how to use computers, and what are the consequences if it is not permissible?

It is not permissible to train workers of a company that produces and sells tobacco, in a way that assists them in their forbidden activity, due to the Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." As for the wages you have already received, you are not required to dispose of them due to your ignorance of the ruling. Ibn Taymiyyah chose the opinion that whoever earned illicit money with the payer's consent, and then repented, may keep what has passed.