Static IP

/ip address add address=192.168.88.1 interface = ether2

PPPOE

/interface pppoe-client add interface=ether1 user=your_username password=your_password disabled=no
/interface pppoe-client print

DHCP

# Get IP address from DHCP server
/interface set ether1 disabled=no
/ip dhcp-client add interface=ether1 disabled=no
/ip dhcp-client print