Hi,
Considering vlan on which you placed your printers, you must determine DHCP ip address on their default gateway.
For example if your printers are in vlan 200,
!
int vlan 200
ip address 192.168.1.1 255.255.255.0
ip helper-address <ip address of your DHCP server>
note that if dhcp server is in another vlan you must have ip routing enabled on your switch.
HTH
Houtan