Open the Chrome browser in Android Chrome. Click on the button "Add certificate". If the certificate does not open automatically, you can also find the certificate in the download folder. A dialog appears in which you can enter your PIN and name the certificate (eg: Tim eBlocker). Please choose "VPN and apps" for credential use. Repeat the process and save the certificate under "Wi-Fi".
For Android versions less than version 6, it is sufficient to save the certificate only under "Wi-Fi".