First, you will need to be a user in multiple companies. If you need to be added to a new company, send the Owner or Admin these instructions on how to invite you.
Click the Company name in the upper-left corner of your screen and you will see all of the companies you are a member of.
Need to create a new company?
While you are logged into Ninety, visit https://app.ninety.io/create-company. This will take you to the page to create a new company, and when you do it will automatically be added to your list as shown above.