Choose the project you are working on, then click on the " TEAM " Tab
Click the " GROUP " Tab at the top left of your screen; below the toolbar.
Click the “+” icon at the bottom left of your screen
Type in the name of the New GROUP, then click "OK"
Once done, Click on the created GROUP on the Left of your screen then check the users you want to add to this group
Creating Groups allow you to share your informations faster, which will save your time when you need to inform your collaborators of any changes in your Tasks.
Also, creating groups allow you to assign the Tasks to a specific Group of Users without having to select them one by one.
Even if you work alone, it is better to create Groups by contractors (Architects, Project Management, Security company, electricity contractor ... )