In the section Certificate Management, you can upload your user certificates that you need in order for HBS to communicate with your backend. This step is NOT NECESSARY when you are using the Hubject CA root certificates - you only need to add them to your trust store and are good to go.
Only .pem and .crt file types are supported for upload.
You can do this via drag and drop or by browsing your directories and selecting the correct file.
In the next article you can read more about the implementation of web services.