How do I import data into oracle 11g r2 using a `.dmp` file and a `.par` file?
The PAR file is a parameter file, which contains parameters for data pump that you don't need to enter on the command line.  Without knowing what those are, we can't advise what you need to use in any detail.

Generally speaking, if you have a parameter file, you just put that on the command line:

impdp user/pass parfile=/path/to/parfile


However, there may be other parameters required.

Assuming you have a parameter file, you need the command line to contain at minimum:

Username
Parfile


To perform an import, you need at minimum these parameters defined between the command line and parameter file:

Username
Directory
Dumpfile
Full OR Schemas OR Tables
(and for good practice, Logfile)


For a basic import, those four parameters between the command line and the parameter file will import data.  Without knowing what you're trying to achieve, anything else is guesswork.