i am trying to link to an oracle db but am having problems.

I have created myself as a user in Oracle
I have created an ODBC connection on the PC where the Access DB is situated.
but when I try link to the data source it says that the odbc couldn't be called.
do I just enter the ip address of the server where it says "Server" or does it need something more?
Obviously I've put the user name and password in there too.

thanks in advance