To build code first, Install node.js https://nodejs.org/en/
To use J-Link debugger install the J-Links Software and Documentation Pack https://www.segger.com/downloads/jlink#J-LinkSoftwareAndDocumentationPack
Once these two items are install in VSCode click Terminal->Run Task->install tools then click Terminal->Run Task->install extensions
If you already have node.js, xpm, and VSCode extensions install you an install the project dependencies at command terminal by typing xpm install
The package.json contains the list of dependencies, ie tools (compiler, make, etc) and libraries needed to build the code. xpm install will install them .vscode directory contains settings for the vscode editor and task commands. xpacks/ directory contains the project specific tools (gcc, cmake, libraries, etc) build/ is the binary builds (release/debug) for the project.