How to configure my 2 router to make them as access points

How to configure my 2 router to make them as access points

I have this broadband and the main wireless router: Main Router
Also I have two other routers and would like to make them as access
points. So All with the same SSID, then the device can choose the nearest
router.
Here are my routers.
Netgear G Router WGR614
D-Link Dir 619
Both of these are connected by cable, to the main router but I used
powerline adapters for the second router as it is far from the main one.
Main router is on DHCP, 192.168.0.1. The second router (D-link) has a an
access point option and I tried it but it disconnects every hour for
couple of minutes and reconnect again. Do not know the reason.
Anyway, what configuration should I do on each of the routers to make them
as described ?
Thanks