restore database from dmp file
version, OS, tool are helping things to help you solve this. 

I guess OS is Windows.
version 9i.
export full.

If this is the case:
connect to the server,
set ORACLE_HOME=/where/is/oracle/home/
set PATH=%ORACLE_HOME%/bin;%PATH%
set ORACLE_SID=ORCL -> or your ORACLE_SID name

imp file=x.dmp logfile=imp_x.log full=y


imp help=y gives some clues about the commandline options.

study the errors. If there is a complaint about the dmp file, read the first few blocks. From those you can find who exported it, what type export it is and even some version info. It is a bit binary but just readable enough to get this info.

tip:

If your data has a real value for your company, hire a real dba to make a decent setup and have someone as a backup. It is easy to build a system that work happily for years and due to hardware issues suddenly become less happy. It's a pity if that costs your company the head. This is regardless for what brand of database you setup.