Project teams are intended to be self-managing, and amongst other things that includes managing commit access to your repositories. When a new repository is created, the PMC should have granted the Project lead the ability to add new team members at will directly in GitHub, without having to obtain any kind of approval (in GitHub terminology, Project leads are created with "repository admin" privileges).
The recommended way to decide on whether a new contributor should be added to the Project Team, is to start a vote on the project issue tracking or mailing list amongst existing Project Team members and use one of the recommended Decision Making - ARCHIVED approaches.
That said, it is critical that the proper legal structures are in place first, to ensure that a new project team member is able to legally contribute to the project. This primarily involves confirming that they have fulfilled the /wiki/spaces/FINOS/pages/75530375 with the Foundation (mainly the FINOS CCLA).
To ensure compliance with the FINOS IP compliance requirements, please ensure that every new team member has a CLA in place before adding them to your project. If you are unsure whether a prospective contributor is covered by a CLA, feel free to contact the Foundation's legal counsel.