Hello,
Do not use repeater mode it will break the authentication process. If the two routers are connected by cable then just use the standard setup method on the 2nd router. You can find the DDwrt install guide here: http://www.hotspotsystem.com/installation-guide-dd-wrt
Be sure to use build 22118 and reset the configuration during flashing.
Build 22118 can be found here: http://dd-wrt.com/site/support/other-downloads?path=others%2Feko%2FBrainSlayer-V24-preSP2%2F2013%2F07-24-2013-r22118%2F
If you are connecting the router by wireless link use this procedure: http://help.hotspotsystem.com/knowledgebase/extend-range-with-wds-wireless-distribution-system
Be advised that DDwrt was not designed for Hotspotsystem and WDS method may not work.
You can also try to configure the first router for the hotspot function and leave the 2nd router in bridge mode.