Just add the (reachable) address of the manager to the remote CAPs config while leaving "discovery interface" blank, select "local fowarding" in datapath and configure your vlans wisely at each site.
MTCNA, MTCUME, MTCWE
There are 10 types of people: Those who understand binary and those who don't.
There are two types of people: Those who can extrapolate from incomplete data
there are two scenarios, if the DSL1 and DSL2 are on the same subnet which is provided by the ISP then yes you can simply reach the other side using Layer3 and specifying the capsman manager ip.
if the DSL1 and DSL2 and not within the same subnet (intranet) and you have a public ip on first side, then simply create a vpn tunnel and others caps a\can join your capsman.
hope this answers your question.