Very NEW to ORacle isn't it?
Ok Follow the steps.
After creating the database successfully and running the req. scripts u r ready to enter into the db but u r not able to do and this is ur problem....
goto C prompt set oracle_sid = ABCD
(ABCD - your db sid)
It gives help or straightaway type this..
C:\oradim -new -sid ABCD -intpwd password -pfile filepath(This pfile is optional)
Run this if there is any error see the help by typing oradim
then goto svrmgr
Still u can not solve the problem then mail me and my mail id is email@example.com
Siva Kumar N.V