To all Freelancer, How do you manage your project and team

I recently got 1 project for app development,
I do not have any experience in freelancing and also not very good with a big project but I am getting paid for learning .

my question is how to manage project and team (now 3 but will increase team size drastically after this project) using free or opensource tools

from To all Freelancer, How do you manage your project and team