Image from Career Contessa
https://www.careercontessa.com/advice/women-sexism-in-the-workplace/
Male allies
Engage men in talking about gender related issues
Women are not effective at persuading men when it comes to gender related issues (Mikki Hebl, 1:40)
Allies speaking up
When one person does it, others take up the action of condemning and condoning long-term (Mikki Hebl, 4:40)
Has an impact on the receiver of the sexism
Question your own assumptions and beliefs
Think if you have ever made an inappropriate comment to a woman or touched them without consent, even just a pat on the shoulder counts
Double check how you talk and if you make sexist jokes
Look out for stereotypes
Urge for companies to take these issues more seriously
Talk to HR, have a conversation with your boss, message your CEO, etc.
You cannot idle by hoping someone else makes a change, if you want something done you have to do it yourself. Even if the issue should not exist to begin with.