Exactly!
If your Cable modem, provides NAT/DHCP services, it is important to set a STATIC IP for the second router.
One that "lives" on the first router's network, but is "outside" the DHCP dolled out addresses...
Then you turn OFF NAT/DHCP on the second router.
Hard wire the second router/AP to the first one, and you're good to go.
The second router's AP will then dole out IP addresses by passing the DHCP request to the first router for servicing.
As far as your machines are concerned they all "live" on one big happy network.
And as an added benefit, because you no longer have to deal with two levels of IP translations, the machines connected to the second router see a DOUBLING of network performance, to match that of machines connected to the first router.