In the left-hand sidebar, click the dropdown menu next to the colored square containing your initials in the top left corner, which shows the name of your personal workspace and other shared or created workspaces.
Click "+ Create new workspace" to open the "Add New Workspace" pop-up, then fill in the following parameters:
Mandatory: Workspace Name
Optional: Workspace Description
Click the "Add" button to create the workspace. You'll be redirected to the new workspace, which will also appear in the dropdown menu with your other workspaces.