What's the easiest way to unrar a file?

Ubuntu by default uses File Roller, which supports the following formats:

7-Zip Compressed File (.7z)
WinAce Compressed File (.ace)
ALZip Compressed File (.alz)
AIX Small Indexed Archive (.ar)
ARJ Compressed Archive (.arj)
Cabinet File (.cab)
UNIX CPIO Archive (.cpio)
Debian Linux Package (.deb) read-only
ISO-9660 CD Disc Image (.iso) read-only
Java Archive (.jar)
Java Enterprise archive (.ear)
Java Web Archive (.war)
LHA Archive (.lzh, .lha)
WinRAR Compressed Archive (.rar)
RAR Archived Comic Book (.cbr)
RPM Linux Package (.rpm) read-only
Stuffit Archives (.bin, .sit)
Tar Archives:
    uncompressed (.tar)
    compressed with:
        gzip (.tar.gz , .tgz)
        bzip (.tar.bz , .tbz)
        bzip2 (.tar.bz2 , .tbz2)
        compress (.tar.Z , .taz)
        lzip (.tar.lz , .tlz)
        lzop (.tar.lzo , .tzo)
        7zip (.tar.7z)
        xz (.tar.xz)
ZIP Archive (.zip)
ZIP Archived Comic Book (.cbz)
ZOO Compressed Archive File (.zoo)
Single files compressed with gzip, bzip, bzip2, compress, lzip, lzop, rzip, xz.

Keep in mind, that this is just graphical front-end, so you still need to install unrar for .rar support;

The unrar package is hosted on the Multiverse repository, so first you'll need to enable the Multiverse repository in Software & Updates;

Then you can install the package either by using Software Centre or by opening Terminal and running sudo apt-get install unrar.

First, run:

sudo apt-get update
sudo apt-get install unrar

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You could read man unrar.

From terminal you can use next command:

unrar e -r /home/work/software/myfile.rar

Or, the following command if you want to preserve the directory structure too:

unrar x -r /home/work/software/myfile.rar

Install unrar from the Software Center or by running the command

sudo apt install unrar