1. Extract the .zip file you downloaded from CodeCanyon.
  2. Upload and overwrite all the files same way you did when you first installed.
  3. Visit http://yoursite.com/secure/update url and click Update Now button.
  4. Once update is completed you will be redirected back to homepage.
Note:
No data will be lost on your site when applying updates.
Important:
Always use a desktop application like FileZilla to upload files to FTP as opposed to web based file managers to avoid issues with corrupted or not properly uploaded files.