Your Project name was created when your project was first set up, it could be your company name or the name of an individual client or project.  If you wish to change this, you must be an account administrator, or the option will not be available to you.

You can find out who are the administrators in your account by clicking on users and looking for users with this icon next to their name    You can then ask them directly to change the Project name

If you are an Administrator, the Project Name field is editable in the settings page.

You can make changes to the Project name, and click on update.  You will be prompted to log out and in again before the changes take effect. Once done, you will see that your new Project name is live throughout your account.