The first thing I would suggest – sign up for the service/product of the company. See exactly what it is. You’ll probably be assigned a salesperson – ask them as many questions as you need. Use the product. Understand what you’re going into – how complicated/technical it is. If it is very technical, then learn the tools that will help get your knowledge to where it needs to be.
At Bright Data, for example, every support manager needs to know JavaScript. Even if you don’t know it when you first come, you will need to learn it by yourself during the process of your work. But it is a requirement.