https://www.raspberrypi.org/downloads/
https://downloads.raspberrypi.org/raspbian_lite_latest
Username: pi Password: raspberry
sudo nano /etc/dhcpcd.conf
At the bottom of the file, add:
#static IP configuration
interface eth0
static ip_address=192.168.1.15/24
static routers=192.168.1.1
static domain_name_servers=192.168.1.1
sudo reboot
sudo systemctl enable ssh.service
sudo systemctl start ssh.service
sudo passwd pi
Enter the new password twice
A more secure thing might be to completely remove the PI user and use another user with the same priviledges. For detailed instructions, see: https://www.raspberrypi.org/documentation/configuration/security.md
sudo apt-get update && sudo apt-get dist-upgrade