first I create a project in the account menu and linked to a repository: Screenshot of the menu of my github account
but when I go to my repository, I found nothing.Screenshot of the project's tab on my repository
How can I merge the account project and the repository project?
Reading on the difference between GitHub repositories and GitHub projects, you have correctly associated at least one repository to your newly created project.
Your profile page (github.com/JulioMelchorPinto
) does show two projects.
If it should show "3", maybe you have associated to the new project a private repository.