This is what I installed on my 2018 Honda Fit EX: https://www.amazon.com/gp/product/B07FXWRH7J?ref=ppx_pt2_dt_b_prod_image#aw-udpv3-customer-reviews_feature_div you can see the pictures I posted in the reviews. There is 2 mini hooks on top of the deflectors, and it use sticky 3M tape. I advise you put it on to try it out first to see where it goes before installing it. So, take your time.
For the dealership they use 3M tape I think and they use clips and pins. https://www.hondapartsdirect.com/oem-parts/honda-air-deflectors-side-windows-08r04t5a100?c=Zz1leHRlcmlvciZzPXdpbmRvdyZsPTImbj1TZWFyY2ggUmVzdWx0cyZhPWhvbmRhJm89Zml0LTUtZG9vciZ5PTIwMTgmdD1leCZlPXZhcmlhYmxl