I would assume you have had the part fitted now but if not see below -
Open the drives door fully.
On the side of the dashboard usually hidden by the door you will see a small notch on the side where you place a flat head screwdriver.
pop the screwdriver in here and pop open the plastic cover (this is actually the fuse box area) The plastic cover is hinged toward the windscreen, be careful as the hinges are plastic! it may take a bit of wiggling to open it enough around the rubber door seal.
Once open you can literally push the air vent from the back and pop it out.
The topic below shows the area very well, picture 3 !!
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