File -> Catalogs

Displays the name of each catalog available for loading, highlighting those that are already loaded. Tap each catalog to select it or not depending on whether or not you want it loaded, then Tap OK. Tap X to dismiss the dialog with no effect.

PSC has its own very compact format, .pdb, and also supports the XEphem format, .edb. Formats for each are available upon request at no charge.