"Using all the seeds (the colored words), try and make a garden of words and join the other gardens below!" ← So for the current garden (should change tomorrow) you need to use 音/おと and 飛び出す/とびだす in whatever you write. You basically just make up a sentence, short story, etc., that contains those words.
If you go to a different one, it would be whatever the coloured words are there. https://app.renshuu.org/games/... ← for this one it would be 青/あお, 赤/あか, and 黒/くろ.