Partioning under E-smith follows generally the same rules as partitioning under any other Linux system (or other OS for that matter).
To muck around with existing partitions on a live system requires a very large brain and numerous years of computing guru'hood. Generally speaking, you don't want to do it.
To muck around with the standard partion sizes etc on a yet to be created e-smith system, you'll need to investigate the kickstart files on the boot disk.
To add partations on the existing e-smith drive or to add additional drives, I'd go looking for documentation concerning such cryptic terms as fstab, fdisk, automount and diskdruid.
As E-smith is based off the RedHat distrobutions and Redhat isn't too far removed 'partition handing'-wise from any other system, general linux documention sources should do the job. (eg. Linux.com etc).
The only spanner that is E-smith specific in this type of works, is the templating system. If your final solution relies on changes to system files, make sure you update the template files that mantain the system files in the first place. Otherwise you could find all your hard work dissappearing on the next restart or upgrade. Documention on the templating system can be found elsewhere on this site.
Regards,
Luke