Hi steve
starting from the left hand side the 2 connectors under the thing that looks kinda like a solar panel is where your solar panels connects to connect positive of the panel to the + and negative of the solar panel to -
the one that looks like the battery is where the battery connects positive to + negative to -
the last on the right that looks like a light bulb is the load connection. you don't need to use this connection.
what it does is it has a voltage cut out so when the battery drops to a set point say 12v it will disconnect the load that is wired to that point.
with out knowing your electrical system I would have one battery for house consumption and the other for engine starting
with the bigger panel with controller charging the house battery.
and a smaller panel with a controller to keep the start battery toped up
If you don't need a starting battery I would just have one battery bank using the 160ah on its own (or upgrading to new battery's) with both panels charging it ideally thought one solar controller , if not possible because of the panels you may be using, use 2 controllers exactly the same set to the same settings.
if you plan to parallel 2 batteries together to make one big bank giving more capacity in ah but the same voltage make Shure the battery's are identical makes and age.
don't connect the 135ah and 160ah together the better battery will equalize to the other one
one panel/controller charging one battery

or
2 panels same controller charging one battery

or
2 separate panels/controllers charging same battery