We provide each of our clients with their own Lab accessible on their own page, such as https://yourcompany.medialab.app. So in order to login, you must know the client's account name you want to access. This is usually https://company.medialab.app. If that doesn't work, you can also find this information in the welcome mail you received when your account was created.
If you are unsure what the exact account name is, please try contacting your system administrator. If that also fails, feel free to get in touch with us through our contact page.