Connecting to oracle database

Thanks. I have tried it but it does not work…

When I leave the SID blank I get the following error: ORA-12504: TNS: listener was not given the SERVICE_NAME in CONNECT_DATA.

When I fill in SID in the database name field, I get: ORA-12514: TNS:listener does not currently know of service requested in connect descriptor.

Could somebody help me out ?

Thanks !