I want to build a Pac-Man game for HTC VIVE using unreal. Any ideas how to begin please???
Not sure what you mean here. But, if you want to start from the very beginning with little to no UE4 experience I would recommend starting with understanding blueprints https://academy.unrealengine.com/Browse/game-development.
If you are new to game development I would recommend picking up an intro to game design book.
If you are new to game design or need a little extra in the howto department. Humble bundle has a good deal on game design ebooks right now and some code books that could be of use for any developer.
Break into the game industry bundle. Humble Book Bundle: Break into the Game Industry by CRC Press
Intro to code, Has some Blender coverage as well, All good stuff to learn. Humble Intro to Code Bundle
And programming cookbooks. Humble Book Bundle: Programming Cookbooks by O'Reilly