Open the iOS Safari browser and click on the button "Add certificate". The iOS settings will automatically open and the profile of the eBlocker certificate is displayed. Click on "Install". In the following dialog click on "Install" again and confirm the adding of the certificate with "Install" again. The eBlocker certificate has now been added in iOS.
Since iOS version 10.3 the added eBlocker certificate has to be activated again. Open the iOS settings and navigate to "General" > "About" > "Certificate Trust Settings". You will find the previously added eBlocker certificate there that can be activated again.