access information_schema

Hi,

I successfully created my first db, a table and some data with psql
7.3.6. However, I can't access the information_schema. In psql I tried
queries like

SELECT * FROM information_schema.columns
SELECT * FROM information_schema.tables

but I get the error message that information_schema wouln't exist.

* Do I have to activate them?
* I don't think it's because of my permissions.
* I use psql 7.3.6.
* How could I list all availabel schemas?
* How do I access information_schema stuff?