You can see a complete overview of the assemblies currently used in your project at the top of the Quantities panel, located under the Assemblies header, so you can see at a glance which classifications have an assembly attached.
How to Import Assemblies to your Project
To add an assembly from your central library to your current project:
Open the Quantities panel on the right side of your screen
Click the Library icon
In the Import from Library window, select the Assemblies option
Check the boxes next to the specific assemblies you wish to add
Click Import