First download the Rasbian zip from here.
Unzip the zipped file.
You need to find your sdcard name. If you don’t now how to, take a look at this post.
Next format your card as Fat32.
Now write the image to the sdcard with the following command. Replace the mmcblk0 part of “of=/dev/mmcblk0” with your drive name.
sudo dd if=~/2014-01-07-wheezy-raspbian.img of=/dev/mmcblk0 bs=4M
It will not display any information until it is finished, so be patience.
Once it is complete, eject it and plug it into your Raspberry Pi and boot it up.