After creating projects, you can set up teams. It is often asked why users can only assign tasks to themselves when creating tasks. The reason is that they have Not set up any teams yet.

After the project is created, a prompt as shown below will ask you to set up a team.

Or you can go to Project-> Team and manage teams there.

Choose users involved in the project and set up the roles for them at the same time, when managing your team. Weekdays and available man-hours must be set up carefully. Generally speaking, a user can not work 8 hours a day continuously or 7 days a week in a roll.