You may or may not have this option depending on your account and the type of company you have setup in Time Portal.
To switch between companies in Time Portal click on your name/company name in the upper right-hand corner of the application. Next, click on Manage Companies in the drop-down list.
This brings you to the companies screen. Select a company from the drop-down list.
This will redirect you to the Dashboard and log you into the selected company’s account. Note that the company name has changed in the upper right hand corner to the company that was selected.