Of course, you must have market experience and promote it through the local science and technology commission, intellectual property office and the Internet.
In addition, China Intellectual Property News also publishes promotional information in each issue (the fee is unknown).
You can also directly search for the mobile phone case you want to promote in Alibaba, where there are many companies, basically all of which have mobile phone manufacturers in China. Come to Shenzhen, a relatively mature place after all, and promote your patent to the managers of the factory. If they think it is necessary, they will pay to cooperate with you or buy your patent.
Besides, it's really difficult to make money from patents, but once we talk about it, we will have a party every night in the future. I design mobile phone software, and I know very well that our company actually welcomes your patent.