I cut mine from 5" gutter screen and attached with the integral screws. For the upper vent intake it's just sandwiched in there.
There's a aluminum edge cap on the gutter screen. To do it the way I did you need every available inch of it. The length long edge cover is just pressed on and can be opened up and removed with a screwdriver.
A few bends to conform and it's done.
No messy silicone adhesives or glue. Screwing & sandwiched would allow easy changeout should it ever be necessary.