As shown in below image you can download your UC firmware for your Snom phone after log on to the above download URL.
Snom 821 phone Web Interface
Before upload the firmware to the Snom phone, you should configure the downloaded firmware to access through web url.
In this setup I am using IIS for this task. After configure the above URL try to access it through web browser.
Now log in to Snom web interface and go to Software Update. Paste the above URL in firmware location and click Load.
Software Update will start on Snom Phone.
Snom Phone is restarting…
You can see the new Firmware version…
New Snom UC Edition Logo.
Log in to the phone interface through a web browser.
UC Account Data feature is available now. Do a System reset by going to Advanced Settings -> Reset
Choose Time Zone.
Choose Tone Scheme..
Log in to the web interface again..
Configure the Network Settings. (DHCP or Static)
Reboot the Phone…
Go to UC Account Data and configure the account data and your are done…!!
I hope you have already configured the _sipinternaltls_.tcp.domainname.com DNS Service record which required to auto provisioning Snom Phone/Lync client.