Here is a quick overview of the OEM HID bulb replacement for the XV (2013ish model) for the markets that sold this variant (ie. not the US).
Firstly the procedure is very similar to other HID bulb replacements for other Subaru models, in particular the 2003-2006 Forester.
On the left of the vehicle you access the bulbs in the headlight assembly behind the washer fluid reservoir filler neck, it is usually not necessary to remove this unless you really want more clearance. On the right hand side you have to remove the air inlet ducting to get access to the rear of the headlight assembly. These are all detailed in many other XV low beam bulb replacement videos so no need to explain in detail.
What is different to the Halogen cluster is detailed below:
Step 1 is to turn off all headlights and remove the key from the ignition. There is high voltage stuff going on in there that you do not want to be a part of.
Inside the engine bay at the rear of the headlight assembly directly inline with the low beam bulb you will find a large black plastic circular lid/cap with warning labels attached. Rotate this cap by hand about 15 degrees anticlockwise and it will pop off (inspect and look after the rubber seal around it's rim).
Behind this you will find the wires leading from the HID ballast to the back of the light bulb with a large metal connector attached to the bulb. Rotate this connector about 15 degrees anticlockwise by hand and it will release from the back of the bulb.
The bulb is held down to the plastic headlight assembly vie two spring wires. At the top of each of these wires is an "ear". Press down (towards the front of the car) on these ears with a finger and move the ear away from the bulb (to the left/right depending on which ear). The bulb is now free and may fall into your hand (take care of the bulb as you remove the second ear).
The bulb can be drawn out of the headlight assembly, taking care not to bump it on anything. IT IS VERY DELICATE. Especially if it is a blown/cracked bulb, there is a high chance it will shatter further and leave little bits of glass inside your light cluster which will require some sort of vacuum cleaning tube contraption to get out.
The bulb is specifically for a reflective lense HID system and has the generic part number D2R
. (This is different from the D2S bulb version that is more common on glass lens based HID systems, like on the 2016 Outback). This is the same as 2003-2007 Foresters with reflective HID lenses.
OSRAM part number 66250 (D2R)
Philips part number 85126C1 (D2R)
Note a section of the bulb glass is blacked out, this is the main difference with a reflective HID bulb vs. other more regular HID setups. My understanding is this prevents blinding of oncoming traffic.
With the new bulb usual bulb safety procedures should be followed, ie don't bump the glass/bulb, don't touch the glass/bulb (use gloves if possible, surgical gloves are best).
The bulb has a cut out in the metal ring at it's base, this should be facing up as you insert it into the assembly and goes into a corresponding slot on the headlight assembly. Line the bulb up as best as possible before insertion to avoid having to rotate the bulb into position.
Hold the bulb in place whilst pressing down on and moving the spring wires over the base of the bulb and into their locked position on the assembly (the first is most difficult as the bulb is not very secure).
Have a look at the inside of ballast connector and line up the centre of the connector with the centre of the bulb. The bulb has plastic tabs sticking out of it which should correspond with slots in the metal connector. Roughly speaking the connector should be placed onto the bulb with the wires pointing out at the 4 o'clock position or in that area such that the connector goes over the plastic tabs.
The connector is then rotated clockwise such that it clicks in place with the wires pointing downward (6 o'clock).
The plastic cap, with rubber seal, is put back in place and rotated clockwise (20ish degrees) until it clicks in place, with the warning labels still the right way up.
Job done, hopefully I have not missed anything. Hope it helps.