User management, or members as it is defined in ACC, can be done under the project Docs -menu. Members -page allows admins to add more users to the project.
Next step is to click Add members, which opens a new page. In this page, add the email addresses of the users who need to be invited to the project.
Once all the needed email addresses are added, proceed by clicking Enter. This will list all of the project members and allows to fill the details for them. The main items are Role, Access level and Products.
Predefining the roles in Account Admin eases the onboarding process and speeds up the project set up. More information about the roles and how to manage those, can be found here:
https://help.autodesk.com/view/DOCS/ENU/?guid=Account_Admin_Roles
Please consider, what type access each user needs. If there are multiple stakeholders involved, everyone might not need an access to all of the files and folders.
Once everything is set up for the invitation, proceed by clicking Send invitations on the bottom right corner of the page.