Account, password problem with sqlplus in Oracle 10g(10201_companion_linux32)

[GMS S]

Hi,
I installed Oracle 10g(10201_companion_linux32.zip).
After extracting got companion directory.
Installing going to that directory "/u01/app/oracle/product/10.2.0/db_1/bin"
I ran ./sqlplus command.

But now I can't type the user name and password because everything is denied.
When installing ,I selected companion option as I got an error selecting the Oralce 10g Database option.I was not prompted for account and password.

There was an option during installation for
i)Wschema
ii)hostname
iii)port
iv)sid

like this.

Now what should I do?Is there any option for creating account and password?
Can anyone tell? 

I am using Fedora 10.
Thanks