Hi Arturo,
why would you?
It is like changing a Windows EXE, you would need the source code to make changes, meaning the Java code from which the app into the APK is compiled from.
If you could just edit the APK and change the app, you could change every app to be your property.
This said, you can decompile your APK with apktool or dex2jar and the manifest will be readable.
After editing it, you can compile and create the APK again, do remember to sign it.
Good luck, but keep in mind the Java source is Appeon's property!
Best,
.m