To make a backup of your certificate in Internet Explorer, please follow these steps:
From the browser menu click on the Tools button and select Internet Options/Content/Certificates. Then in the Personal tab, choose your certificate and click on the Export button:
By clicking the Export button, a Wizard opens, which will guide you through the procedure of exporting a certificate. To continue, click Next, then choose „Yes, export the private key“. Choose a .PFX format in which the certificate will be exported and choose to export the root certificates:
Enter a password to protect the private key. The password is only known by you, please remember it or write it down in a safe place!
Enter a file name and location to which you will export the certificate. At the end, you will get a message for succesful export.