New eagle library: reuse standard package & symbol
You can just copy a package from another library into your own library and edit it. Are you asking how to copy between libraries?
- Open your own library (the one you want to copy to).
- Then bring the Control Panel window to the front (leaving your library open in the background).
- In the list to the left, expand Libraries and expand the name of the library you want to copy from.
- Locate the package or footprint you want to copy, right click it, and select Copy to Library.
- Bring the window with your own library to the front, locate the newly copied package and edit it.