if you use apt-get install rar you can get it that way, then you just need to read the man page, but here is the extraction command:
rar - archive files with compression
rar <command> [-<switch 1> -<switch N>] archive [files...]
e Extract files to current directory. Does not create any subdi-
so you would just:
rar e /location/of/file
and wait, it will extract your .rar file into the current directory.