GAME HELP— SUDOKU & BOO

Just wondering about these TWO games (for now).

How does one LEARN TO PLAY SUDOKU? I get the “rules”… I just don’t know how to go about it. Not one that I ever played or was interested in.

I have enjoyed the BOO GAME… Got to level 11, 2 stars… Thought I was doing well, but then read how many of you got to level 20 (more than once!)…. HOW?

I try & try & can’t even get the score that got me the 2 stars.

Thanks to any who are willing to help.