I want the Arduino to check constantly and when the correct frequensy occurs I want it to give me a signal.
This what I thought, sensor light-to-frequency. But after visiting product web-page, it turns out it's Not the case. Sensor outputs digital stream I2C format, basically you need to write a software DRIVER for arduino to communicate with device. Task is too complex even for experienced programmers, definitely not for beginners. Your hope only too google if someone already create a library, for exactly same sensor or something close in hardware - software implementation.