The preferences dialog can be opened by the toolbar or through the "Program" menu. The dialog is divided into seven tabs described in the following text.
The "Update all subscription at startup" check box allows you to control the update behaviour right after startup.
Folder Display Settings: With these check boxes you can control what Liferea loads into the item list when you click a folder. The default behaviour is to load all unread items and to hide all items you've already read.
Usually you will want to enable both options as this allows to quickly read through all unread items of a set of feeds.
This tab allows you to configure how Liferea should handle enclosures. If you are still unsure what enclosures are about please read the Enclosures/Podcasting section first.