First we have to download the package into the box:

wget http://www.rarlab.com/rar/rarlinux-x64-3.8.0.tar.gz (for 64 bit os)
wget http://www.rarlab.com/rar/rarlinux-3.8.0.tar.gz (for 32 bit os)

Opening the package:

tar -zxvf rarlinux-x64-3.8.0.tar.gz (for 64 bit os)
tar -zxvf rarlinux-3.8.0.tar.gz (for 32 bit os)

And

cd rar
./unrar
cp rar unrar /bin

Enjoy rar on your box.