When a new version is released, I upload the code on Codecanyon.
Codecanyon send you a notification, so you can download the new version.
Before making the update make backup of AdAdmin folders and database (this is a standard security tip).
Since version 3.994 the update process is extremely simple.
Just copy all files over the old ones and go to the url of your installation.
Update process will run automatically with this screen:
Click on proceed to complete the update process.
If a problem happens, please contact support.