Arduino SSR 5V DC (Mager GJ-3FA-L)
Re your thoughts on wiring it, I think your second diagram has the output polarity reversed. The (-) should go to the power supply and the (+) to the load. 

If I misinterpreted what you meant by "IN" and "OUT", then the other diagram is reversed- (+) should go to the power supply and (-) to the load. 

The diagrams are not backwards. This one: 



Is looking at the bottom of the SSR (pins pointing at your face) as if you rotated the relay 180° in the top photo about the X-axis (label would not be visible). 

This one: 



Is looking down through the top of the relay, with the relay in the top photo rotated about the Z axis 180° (writing on the label would be upside-down).  

The output will be normally open  (no voltage applied to the input). When sufficient voltage/current (at least 6mA at 3V) is applied, it will close. Note that the "off" leakage specification is quite high (1.5mA). 

The SSR incorporates 1500V isolation so you can use it either as a high-side switch or a low-side switch, as you have shown (except for the polarity). 

Edit: The schematic you linked is wrong-- the transistors drive the input of the SSR with series and shunt 10K base resistors. The collectors of the transistors go to the SSR control inputs. They reversed collector and base on each transistor. 



The other two 1K resistors are for indicator LEDs that are in parallel with the SSR inputs. The SSRs can accept 3~32V in but the LEDs need a series current-limiting resistor each.

The transistor drive circuit is only required if your drive circuit cannot supply at least 3V with 6mA current. Not a problem for most 5V logic. 

The LED indicators can be omitted if you don't need visual indication (plus they draw additional current from your drive circuit- a few mA more, so the requirement is more like 10mA).