Whether you just created a library or were invited to a shared library, adding assets is straightforward in Adobe XD. Since asset types can vary across the Creative Cloud suite, certain asset types are only accessible from the applications that use them. Components created in Adobe XD for instance are currently usable across other Adobe XD documents.
From Adobe XD assets such as Colours, Character Styles, Components and Graphics can be added to a Creative Cloud Library. To add any of these items, select the element to be added to the library. Ensure that the Libraries panel is open and the desired Library is selected.
Next, click the + button at the bottom of the panel, which will open up a menu allowing you to select which type of asset should be added to the library.
From here, select which type of asset should be added to the Library. For instance, if you select a shape or vector graphic you can choose to either add the Fill or Stroke Colours, the Graphic itself or all of the above. Once selected that element will be added into the Library and be available for use straightaway.