Step 2. Hit Volume Up to enter ODIN Download mode then connect a micro-USB cable from your S3 to your computer.
Step 3. Next, download the appropriate TAR CWM recovery file on our Galaxy S3 CWM/TWRP Recovery page.
Step 4. Next download ODIN zip file and unzip the files.
You should get a folder called Odin3v185 with two files like below.
Step 5. Double-click on “odin3v1.85.exe” to start ODIN program.
Step 6. You should see a yellow-highlighted box with a random COM number. If you don’t see this, you don’t have proper drivers installed. Download and install Samsung Galaxy S3 USB Drivers.