Edit your network configuration file

sudo nano /etc/network/interfaces

It should be similairto this configuration

auto ens18
iface ens18 inet dhcp

Replace the above two lines to use statc IPv4 instead of DHCP

auto ens18
iface ens18 inet static
 address 185.62.56.69
 netmask 255.255.255.0
 gateway 185.62.56.1
 dns-nameservers 89.207.128.252 89.207.130.252

Apply the changes

sudo systemctl restart networking.service