First, make sure your iPod and iTunes are at the latest software versions by selecting Check for Updates in iTunes Help.
Select your iPod from the devices list in the left pane of the iTunes window. This will open your iPod's details in the main pane, normally showing the summary information like the iPod's name and serial number etc. At the top of the main pane is a series of tabs (Summary, Info, Apps, etc). The far right one is normally Photos. Click on Photos to bring up the photos main pane. In here you can select which main folder you want iTunes to sync photos to your iPod from. If you then select All Folders it will sync every photo in every folder within your selected main folder (does that make sense?). If you select Selected Folders you will then be presented with a list of folders within your main folder and you can choose which folders to sync.