Below are the commands for configuring DHCP in a router/switch in Cisco Packet Tracer.
Replace POOLNAMEHERE with your DHCP pool's name.
For the network command use the Network's address and subnet mask
For default-router should be the default gateway of that subnet.
ip dhcp pool POOLNAMEHERE
network XXX.XXX.XXX.XXX XXX.XXX.XXX.XXX
Rinse and repeat for more pools. Use the command below to exclude the default-router's IP address or any other IP addresses from the DHCP pool to avoid DHCP address conflicts.
ip dhcp excluded-address XXX.XXX.XXX.XXX
You may need a helper address if your DHCP server is outside of the broadcast domain of the subnet the node is in. Command below goes on the port of the default gateway of that subnet. The IP address should be the DHCP server's address.
ip helper-address XXX.XXX.XXX.XXX