open my Computer ==>
right click inside my computer and select properties ==>
Click on Advanced System Settings ==>
Environment Variables ==>
from the System Variables box select "PATH" ==>
Edit... ==>
then add this at the end of whatever you find their
;C:\PostgreSQL\9.2\bin; C:\PostgreSQL\9.2\lib
after that continue to click OK
open cmd/command prompt.... open psql in command prompt with this
psql -U username database
eg. i have a database name FRIENDS and a user MEE.. it will be
psql -U MEE FRIENDS
you will be then prompted to give the password of the user in question. Thanks