Firstly edit the netplan config file

sudo nano /etc/netplan/*.yaml

Format

     version: 2
     Renderer: NetworkManager/ networkd
     ethernets:
        eth0:
          dhcp4: yes/no
          addresses: [IP_ADDRESS/NETMASK]
          gateway4: GATEWAY
          nameservers:
              addresses: [NAMESERVER_1, NAMESERVER_2]

Example for DHCP

     version: 2
     renderer: networkd
     ethernets:
        eth0:
          dhcp4: yes

Example for static IP address:

     version: 2
     renderer: networkd
     ethernets:
        eth0:
          dhcp4: no
          addresses: [192.168.1.1/24]
          gateway4: 192.168.1.254
          nameservers:
              addresses: [1.1.1.1, 8.8.8.8]

Apply the new config

sudo netplan apply