Issue regarding connectivity ASP.net with oracle...

Hello sir,
I am facing problem when i connect Oracle 10g to my asp.net project ..



when i go to tools in Visual Studio>tools>connect to database>oracle database
then in dialog box it ask for server name ,user name and password .
when i do this i am getting only host name and it is not working.
Should i create a database in Oracle as in Sql Server??

and i don't find my server name 
it is showing error-
ORA-12154:TNS:could not resolve the connect odentifier spedified.
please help me with the whole procedure how i can do this bcoz i am a beginner in this field