I'd greatly prefer a GUI. It seems like a command-line tool would be incredibly tedious when creating tables, modifying them, filling them with data, etc. Thanks.
normally, your application programs do the data filling part, manual data entry direct via sql is fairly uncommon.
anyways, the GUI is pgAdmin, and you can create a database by opening the server, and selecting 'new database...', give it an owner, etc. then open that database, find hte Public schema therewithin, and create your table(s) in that schema...