How can i add a custom property to class .apexcharts-tooltip?

[chevyweird]

I need to set a custom property to standart apexcharts class .apexcharts-tooltip. I found it in dom tree

then i find a apexcharts.css file with all these classes, but when i change something on it, it doesn't work. How can i change it in apexcharts files, or set a custom class from my working file?