Follow these steps for uploading an extension into chrome web store.

 

Step 1 : Go to https://chrome.google.com/webstore/developer/dashboard and login

Step 2 : Go to dashboard and click on Add new Item and accept google t&c

Step 3 : Upload zip file of the extension

Step 4 : Fill the form in next page and publish the extension

For more information follow this link https://developer.chrome.com/webstore/publish