Step 1: write your code
Step 2: chrome://extensions/
Step 3: Choose developer mode
Step 4: Click button Load unpacked to test your extension
Now you see your extension here
Step 5: Click button Pack extension to pack your extension
Browse Extension root directory
You can choose your Private key file
Click button Pack extension to create .CRX file
Done, now you have 2 files: myaddons.crx and myaddons.pem in your desktop