By modding, do you mean editing stats?
@Akki182 posted a tutorial video in the Tricks, Guides, & Injections sub-forum. To summarize, you'll need to use APK Editor Pro (which can be found in the same sub-forum inside the thread by
@Axiom on unlocking CoG Games). With that app, choose the CoG games you want to mod. There's several ways to do this depending of the way the writer did the game coding. In general, you'll need to change the stats in startup, stats, or the prologue/1st chapter. Another thing that I usually do with APK Editor is to look for how to achieve achievements and seeing what each choices' effects.