To Create a shared group library...
Step 1: Go to the "+" icon at the bottom left corner of the web app and select "Create Group Library"
Step 2: Give your Library a name and choose who'd you like to have access to it. You can select all team members or add specific people.
Your new library will automatically be created and you will see the new folder open and ready for you to add things to it.
You can always edit folder details including members by clicking the gear icon to the right of the folder name.