If you have a company or companies in mind start with their HR department. They are the ones who usually organize such trainings and activities. Also, they have access to all of the company’s employees and they can help you promote your ideas. Have a proposal ready to present them because they want to know exactly what they are getting into and it helps them promote your classes/events more efficiently. If you know someone in that company, have them introduce you to the right people because it can save you a lot of time and money.
Many companies offer perks to their employees and you can be one of them. Health fairs are popular and participating in some of those could help you promoting yourself and services. You can also be a speaker in one of their lunch and learn programs where you could educate them about a toping of your choice.
I hope this helps.