Step 1: First update your android Message app to it’s latest version (above version 3.3.043), from the Google Play Store.
Step 2: Now open the app, and click on the three-dots which you can find on the top-right corner of the options menu. Next select Messages for Web from the dropdown menu and click on the “Scan QR Code option”.
Step 3:Now from your PC’s web browser log on to https://messages.google.com/web/authentication?redirected=true
Step 4: Scan the QR code shown on the PC’s screen using your phone, and you are good to go.
Step 5: In case you use a PC regularly and would need to perform these steps every now and then, you can toggle on the “remember this computer” option.
Step 6: You will immediately see a notification “Connected to Messages for web” on your smartphone once you have completed the above mentioned steps properly, you can also find a list of computers from which you have signed-in from the “Messages for web” settings.
You can also download the messages for android software directly from the Windows store if your PC is running at least on the Windows 8/8.1/10 OS.