You can log in to your Synology NAS through a browser using its IP address or via the Synology Web Assistant at find.synology.com on the same network.
For shutdown, DSM has a software option in the user menu, and the physical power button on the device also supports a safe power-off sequence.
Quick Answer
Type your NAS IP address followed by :5000 in a browser, enter your admin credentials, and click Sign In to access the DSM desktop interface.
Method 1: Log In via IP Address
Open any web browser on a device connected to the same network as your Synology NAS and type the NAS IP address followed by the port number 5000.
For example, if your NAS IP is 192.168.1.100, type 192.168.1.100:5000 into the browser address bar and press Enter to load the login page.
The DSM login page will appear. Enter your administrator username and password, then click Sign In to reach the DSM desktop and management interface.
Method 2: Log In via Synology Web Assistant
If you do not know the IP address of your NAS, open a browser on a device connected to the same local network and visit find.synology.com.
The Web Assistant will scan the local network and display all connected Synology devices. Click Connect next to your device from the results list.
The browser redirects to your NAS login page automatically, where you enter your credentials and sign in the same way as the direct IP method.
Method 3: Shut Down via DSM
To shut down from inside DSM, click the user icon in the top-right quick access bar on the desktop to open the user dropdown menu.
Select Shutdown from the dropdown. DSM will display a page indicating the device is shutting down. The process takes about a minute to complete fully.
Method 4: Shut Down via Physical Button
If DSM is unreachable, use the physical power button on the front panel of the Synology NAS device to initiate a safe shutdown sequence.
Hold the power button for at least 4 seconds until you hear a beep from the device. Release the button after the beep and the NAS will begin powering off.
Wait for the status LED to turn off before disconnecting power. Unplugging before shutdown completes can corrupt the file system on your drives.