A Note and a Caveat
There are a couple more things you should know about shared libraries. First, you can share fonts. If you have a font on your computer that needs to be embedded into several Flash movies, you can turn the font into a shared asset and use it in all of the other movies. To do this, you select the Options menu in the Library (top-right corner) and choose New Font from the list. Then just choose the font you want to share, give it a name, and call it a day.
The one caveat of using shared libraries for online Flash content is that they need to be downloaded completely before any assets inside of them can be used by other movies. Because of this, it's important to keep the file size of shared libraries as low as possible. If you had a hundred assets in a shared library, all of them would need to download before other movies could access them. That would be bad. Try to minimize the amount of shared assets whenever possible.
Until next time, happy Flashing!