As a partner, you have the option to create new projects for your client organizations.
To do this, nothing could be simpler; just go to the Projects page of the desired organization and click on "Add a project".
You can then name your project, and if you wish, activate the validation workflow within the Verification module (How to use the verification workflow?)
Your project is now created! But the work is not finished.
You must now initialize a repository, that is to say, build the structure of your project.
We detail everything in this article: How to initialize a new repository?