Re Create APK File

Hey Everyone ! Guys Firstly If I Posted In Wrong Section Im Sory For That But I Need To Some Help. I Got Source Codes Of An Android APK File I Want To Edit That As I Want. There Is "Class Files" I Have Edited In Text File And Converted Back To Class File But IDK If It Works So How Can I Edit That Codes In A Class File ? And Second After DoThat How Can I Make It APK Again I Mean How to Re Create APK File With That My Own Codes. Someone Can Help Me ? Its So Much Important , Thanks Everyone