The picture must not be displaying, but it's like the top stone of an arch or part of a rainbow 🌈 that represents the windshield and a whale spray across it 🐳. Sometimes the cap is blue. If you look on the thingy near the steering wheel that activates the sprayer it should have the symbol on it as well.

As for how often to check, it'll depend on how much you use it. I'm in an arid area so I rarely use mine and it gets filled when I get my oil changed. If you're not sure, you can try once a month and increase the time between if it doesn't need filled in that time period. Some newer vehicles may have warning lights that are the same symbol for low levels in which case you don't have to worry about it at all until it's lights up.