Navigate to the “Projects” tab
There you can see all the projects. Click on a specific project
Click on “Teams” tab
Then Click on the “+Add” button at the right corner
The Team you want to add is not already setup at Organization level, so turn off the "Pick from Global" toggle button.
Enter the Team name
From dropdown select which category that Team belongs to (Consultant, Contractor, Vendor, etc..)
Select the checklist (single/multiple) then click on "next" button
Click on +Add user to add user details
Fill the “Add Team user” form and click on "Add"
(Note: Similar way you can add multiple users in a same Team)