The easiest way to use this project is to not use it at all - at least, not directly. Briefcase is a tool that uses this template, rolling it out using data extracted from a pyproject.toml ...
In general it is not good practice to add UIKit elements to SpriteKit games, all your UI should be done using SpriteKit APIs (SKSpriteNodes, SKLabelNodes, SKNodes etc) directly in the relevant SKScene ...