Hello
First welcome to forum, hope you have much fun with KB series.
About installing mods you need to go to your game folder expl - c:\games\kings bounty\armored princess\sessions\orcs\ ... there you`ll find 2 archives .kfs type locations.kfs and orcs.kfs.
Open/extract orcs.kfs with winrar/winzip and in that new folder copy/replace files from mod you mentioned (better chests digging) with those already in folder. Close folder and start game, that`s it.
If you get any problems, just delete folder orcs that you extracted, and leave original orcs.kfs archive and game will take it`s data from it.
Good luck