The Repository permission of GitHub's fork will be changed from public to private

When we fork someone else's project on github, the default is public, that is, public. If we want to change it to private, it is not allowed, but I will change it.
We can modify the private permission in the following way.
First: Create a private warehouse by yourself
Then: After the creation is complete, there will be an import code prompt below, we click on it, and then write in the address of the warehouse you want to fork.
Finally: Click Begin import and wait for the import to complete.