Need help to post article at private blogs

Hi,

I saw many people use private blogs to increase backlinks. I have seen this process really worthy.

I also have my own dating website and want to follow this method only to get more valuable backlinks. But I am not able to understand how I can post my articles and comments at these kind of blogs, i.e.,

https://pastryshoeblog.com
https://www.covantagetemplates.com
https://www.infantconstipationcure.com

I would like to appreciate your thoughts.