You start with opening Microsoft Internet Explorer. In the "Internet Options", found under the tools dropdown in Internet Explorer, you can see the following in the "Content" tab: 

In this, you select "Certificates...". This opens the following dialog:

In this dialog, you select the tab "Intermediate Certification Authorities", in which you select the certeficate associated with your domain. In this case, it is the CIBIT certificate. After selecting the certificate, you click on "Export...". After a welcome screen (click "Next" on this screen), you get the following screen:

In this screen, you select "DER encoded binary X.509 (.cer)" and select Next. In the following screen you can type a name for the certificate. After clicking Next, you see the following dialog:

The dialog provides an overview of all the properties of the certificate.

Installing the certificate on the mobile device

Now that we have obtained the certificate, we have to install it on the mobile device. We start by copying the certificate from the desktop to the device. After copying the certificate to your mobile device, you can see the file in your file explorer. After tapping on the certificate, you see the following dialog:

You tap "Yes", after which the certificate installs. You can check this by going to the "Settings", "System" settings, where you can find the "Certificates" application. When you open it, you can see the following screen:

In the overview of the root-certificates you can see the newly added certificate, in our case the CIBIT certificate.