Which version of the “VisualTestingInKatalonStudio” project are you looking at? I presume you are looking at v1.9.2 or earlier. The most up-to-date version is v.1.10.9.
At the version 1.10.0, I made a significant change to this project. I introduced a Gradle plugin visualtestinginks, which makes it very easy to “enable your own Katalon Studio project to perform Visual Testing — twins mode and chronos mode”. I changed completely the method to make your own project to be capable of Visual Testing. Therefore I DELETED the document “Step by step instruction” as its content is no longer valid as of v1.10.x.