Companies only exist when they are linked to a person on the account. So, to create a new company you'll need to first add a new person to your account.
You can do that right from the Home page. Just click 'Invite people':
Create a company by typing the company name in the "Company/Organization" field of the first person that you want to add to the company.
This creates a company that you can now add other people to.
If someone already exists on the account, you can still add a new company. This is something only an Admin or Owner can do through Adminland:
- Go to Adminland
- Click on the first option to "Add/remove people or change their access"
- Find the person whose company you want to change, and click "Edit info" in the ••• menu button
Click the tiny "X" next to the current company name, type in the new one, and click to save changes:
This is something only account admins or owners can do. You can see who to reach out to for this when you go to your account Home page, then click on Adminland on the right hand side of the page.
If you're an admin or owner, this guide goes over how to rename or delete a company.