You have to do this
1. change the file extension from .apk to .zip
2. extract the contents of the .zip file to a directory, if you use winrar or 7zip or similar, you usually can just right click on the file, then it will extract to "xxxxxx\" where xxxxx would just be the name of the file and a directory where that file is located will be created.
3. Go to the directory that was just created and then go to the RES folder
4. Scan through the different folders within RES and find the files you will need to change
5. Download GIMP (free) or acquire Photoshop (ripoff price)
6. Use GIMP or photoshop to edit your .png files, then save to same directory
7. Do this for all files needed, also read up on .9.png files, if you don't edit them properly before sending them back to your phone, your keys might be coming out looking stretched.
8. Once you edit all files, and also note that some files might exist in other directories that are the same as in another. Same filename, check the dimensions (pixels example 54 x 47) and if they are the same just copy then paste it over from the other directory and overwrite that file that wasn't edited, that way you don't have to do it twice
9. Use your program 7zip or winrar or similar and compress the files again. Easy way is to go back to the root of the folder where it shows all the files you extracted within the folder you created, select all files in that folder, right click, then choose add to archive, and make sure you create a zip. Change the file extension from .zip to .apk
10. Push to phone and pray it looks right.
