BELOW WE MAY GET STEP-BY-STEP SCREENSHOTS,

Step 1 - Click on "Internet Explorer" icon from the task bar to open browser.

Step 2 - Click on "Download the Windows Device Recovery Tool" from website "https://support.microsoft.com/en-in/help/12379/windows-10-mobile-device-recovery-tool-faq" once it opens in the browser. After download completes, install the application.

Step 3 - Double click on "Windows Device Recovery Tool" shortcut located on desktop to run the application.

Step 4 - Connect "Microsoft Lumia 550" to PC via USB cable.

Step 5 - Windows Device Recovery Tool will detect the phone. Verify and Click on it.

Step 6 - Please wait for a while, it will fetch the firmware version from the device.

Step 7 - Verify the version difference, click on "Install software".

Step 8 - Read the message carefully, do all needful and once confirmed, click on "Continue" else click on "Cancel".

Step 9 - Select appropriate option.

Step 10 - Downloading will take place.

Step 11 - Sit back until package download gets complete and updates the phone.

Step 12 - Once Software package updates successfully, click on "Finish".

Step 13 - Repeat the process up to step 6, in-case need to verify the version.