Hey there. I found a good kw and niche for me. but i cant understand how to let google know that i have this keyword for my cpc?
you need to build a site around that good keyword, then do seo for the site to drive traffic. Keep updating the site with fresh content and drive organic search traffic. Thats all - Google will know your site and if you have the ads, you can monetize!
Keep writing quality content around that keyword, Google is smart enough to understand what your site is all about!