Pre Requisites

Check the DHCP status

sudo service dhcpcd status

If it is not activated, run the command below:

sudo service dhcpcd start
sudo systemctl enable dhcpcd

Identify Router IP Address

netstat -nr | grep default

Identify DNS Server

sudo vim /etc/resolv.conf

Adding the static IP Address

sudo vim /etc/dhcpcd.conf

interface <wlan0 or eth0>
static ip_address=<STATIC_IP_ADDRESS>/24
static routers=<ROUTER_IP_ADDRESS>
static domain_name_servers=<DNS_IP_ADDRESS>

Reboot

sudo reboot