I want to upload the extension created by myself, ExtensionsIndex/.github/PULL_REQUEST_TEMPLATE.md at main · Slicer/ExtensionsIndex · GitHub
Is this the tutorial about how to making it?
Yes that checklist is helpful; there is also this description of the release process: Extensions — 3D Slicer documentation
Thanks, I also wonder how to do it offline to just test the extension on my own computer, is there any tutorial?
How to build, test, and package the extension are all described on the same page referenced above.