How to water
Plants need water to grow. Press and hold the water button and try to keep the bar at the top in the green area. The rain drops are watering the seeds that you’ve planted.
Come back later and water your seeds again before the bar reaches the red zone. When it gets to red, that means the seeds have dried out.
If the bar goes in the yellow, you’ve overwatered your seeds. They will wilt, but won’t die. Just wait until the bar slides to the green and your seeds will be fine.
You will have to repeat this process depending on the seeds you have planted. Some might have to be watered many times before they are fully grown.
Here is a video showing the basics: