Why doesn't my game function properly after building it?

I'm very new to Unity and I have just started learning C# for it. And I'm just copying from a tutorial and then I wanted to do myself a Starting Screen that has the normal help and play buttons. But when I was done doing the starting screen and the help screen I did build the game but it didn't function at all. The buttons didn't work at all. And I did search this already on this site and I did look from the output_log but it was normal. I really would like some help.