This resource explains how to install the Raspbian operating system and set up a Raspberry Pi. You will need another computer with an SD (or MicroSD) card reader to install the image.
Install Raspbian Download the Image Raspbian is the Raspberry Foundation’s official supported operating system and can be downloaded from the Raspberry Pi website Downloads page.
After downloading the .zip file, unzip it to get the image file (.img) for writing to your SD card.