Model : Archer C5

Hardware Version : Not Clear

Firmware Version :

ISP :

Hello,
I would like to the Archer C5 only as W-LAN access point. My configuration is: DSL modem / router provided by Vodaphone having DHCP active. Now I'd like to setup the Archer C5 in my living room as addtional W-LAN access point as the W-LAN provided by the DSL modem is too weak. But I'd like all client to be in the same IP net (defined by the DSL modem).
I found a couple of instructions on the internet saying you should set the WAN address to an address in in the network configured on the DSL modem (192.168.2.*) but outside the DHCP range (192.168.2.100 - 192.168.2.200) and then deactive DHCP on the Archer C5
But t
1.) What should I configure as the IP on the LAN then?
2.) When I deactivate the DHCP on the Archer C5 the clients don't see the DHCP server of the DSL model and hence get no IP address
Could someone please provide a step-by-step instruction maybe with screen shots and PRECISE wording?

Thanks a lot in advance
Hansjörg