Sometime to use Skype for Business in an intranet there is the need to install a firm certificate: it may even happens that Skype for Business works when your PC is connected to Internet (if you have required the proper rights) even without installing the certificate but that is required if you are connected to the intranet!

Having the certificate file (.cer) and possibly a command file (.com) that simply install it (certutil -addstore Root NameCa.cer), the installation is very easy as shown in the following screenshots.

1. First you have to run the command prompt (available in C:\Windows\System32) as an administrator and go to the directory where there is the certificate file and the command file
2. Run the command file in order to install the certificate (e.g. NameCa.cer)
3. Possibly you need to restart Skype for business app in order to let it properly connect now using the just installed certificate.

Run the command prompt as an administrator

Run the command file in order to install the certificate

A possible alternative way, could be possibly to right click on the certificate file and choose Install Certificate.

Alternative way: right click on the certificate file and choose Install Certificate