I need to wire this switch, but I have no idea how. I thought I was buying a normal 3P rocker switch :)
The power source is 12v battery and the load is LED flashlight.
It looks like you can control the LED of this switch separately from the actual switching. If you apply +/- on the "3" contacts, then it will light up the LED on the switch. Then "1"/"2" are the contacts for the switch, simply giving you an open/close.
Unfortunately, it doesn't look like it is what you wanted if you were looking for a 3 position switch. It can be hard buying switches without fiddling with them first to make sure it's what you want.
I thought I was buying a normal 3P rocker switch :)
simulate this circuit – Schematic created using CircuitLab
Figure 1. (a) A 3P (3-pole) switch would have three independent contacts. (b) A 3P2T (3-pole, double-throw) switch would have three changeover contacts. (c) What you've got and how to wire it.
You've purchased a 1PST (one-pole, single-throw) switch with built-in isolated indicator.
It's an SPST rocker switch with a 1.85V 10mA LED as the status indicator.
The switch terminals are 1 & 2 and the indicator terminals 3+ & 3-.
The value of the LED voltage dropping resistor R would depend on the supply voltage.
Here are the cut-out details for mounting the switch.