The soonest bonus puzzle you'll be able to play is Bonus 1 after completing level 10 in World 1.
To get 3 stars in this puzzle you need to use four 3-letter words, gain 250 points and use one themed word.
-There are many 3-letter words in this puzzle. Some examples I used are dup, pud, sae, per, ser, gin, lin, and many more.
-As for the themed word, the theme was shopping so I used the word "sell".
-You'll most likely gain 250 points along the way, but if you didn't just keep guessing words until you get enough points. (tip: rotate the board if you can't find any).