I have installed postgresql long time ago but since I have installed it I cant see any postgresql in my pc. It looks in synaptic that I have installed it. Where is my postgresql? How can I use it? Shall I use console?
If you're expecting a big whizzy application to be listed in the Apps menu then you're obviously a beginner to postgresql. If you want a graphical admin interface then you can install pgAdmin (if not already added as a "suggested" package to go with it).
Otherwise you can log on using the "psql" command-line client. See the docs on postgresql.org for basics (eg connecting to template0/template1, creating a new db, setting up users etc), or maybe also installed on your PC with it in /usr/share/docs or somewhere. In ubuntu by default it keeps the database in /var/lib/data/postgresql/8.1/main so make sure that'll have enough space or re-init it somewhere else that does (and edit the config appropriately). It's all a case of RTFM really.. You can start/stop/check the status of the server with /etc/init.d/postgresql-8.1 in the same way as other init.d scripts tend to work (or probably using the graphical services control dialog thing too).