How to set up Postgresql?

Question

PostgreSQL

Hello.
I'm trying to deploy a Django project on AWS.
I install Postgresql:
sudo apt-get install postgresql postgresql-contrib
After that I do:
sudo su - postgres
Then I try to create a database using:
createdb mydb
I get:

createdb: could not connect to database template1: could not connect to server: No such file or directory
  Is the server running locally and accepting
  connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

What to do with it? Google solutions didn't help