down vote
	

I think the previous answers are out of date.

In order to import a .aar library:

    Go to File>New>New Module
    Select "Import .JAR/.AAR Package" and click next.
    Enter the path to .aar file and click finish.
    Go to File>Project Settings (Ctrl+Shift+Alt+S).
    Under "Modules," in left menu, select "app."
    Go to "Dependencies tab.
    Click the green "+" in the upper right corner.
    Select "Module Dependency"
    Select the new module from the list.