If you haven't already done so, download the MiPermit app for Android devices from the Google Play Store.
After you launch the app you are greeted with the default screen, from here you can open the side manu and select Login menu item. On the login page, enter your Username and Password to login. If you have forgotten your login details please use the 'Forgotten' button provided on screen, or see the 'Reset Password' help article.
If you do not have a MiPermit account and wish to just pay for parking and have none of your details saved, you can use the Pay & Stay map to do so without logging in.