There are examples of how different symbols are split across parts in the sample library shipped with the installation, take a look in there and also read the documentation with the product to help fill in your gaps in knowledge. The method is as Charles stated above and the documentation will help you with the method.
The sample library can be found here: Install path/SDD_HOME\standard\examples\SampleLib2007
I have moved this to the Library and Data Management sub-community - you will find more relevant information regarding libraries on this community.