When you purchased the template you were given the full source code of the Android App and of the server side. We give you the freedom to customise any of the source code files for your project's needs.
From time to time, we release a new version of the source code adding features and fixing known bugs. Since you might have edited some of these files, you might not be able to simply drag and drop the new source code. So we suggest 2 ways to upgrade your source code to a new version:
1) Start Fresh.
Download the new template for free and start the customisation fresh. This is especially ideal if you only changed the strings.xml, configurations.java & some images.
2) Update your Project
Use a software like winmerge (http://winmerge.org) to scan your project against the new updated source code and perform the required changes on your source code.
In any case, if you replace any files, make sure to update any package names to your package name,
Take a look at the change log on the template codecanyon page. If you do not require the new features of the template and the present bugs do not effect the project, you might opt to not update your project for now.