Ren'Py works the same way for macOS, Windows and Linux.
Matching the Build Dates
The version of Highway Blossoms on itch.io is 2.5.4 at the time of writing, but you want the 1.1.1 version of the patch. The game itself doesn't tell you what build version it is, but the itch.io interface does.
Here's how you can tell: itch says the build is dated Sep 30, 2020. The patch folder contains a .karentools-build-info text file with the build date for the patch. Make sure this date is the same as the date listed on itch.io.
The date for the 1.1.1 patch is:
ビルド 2020年09月30日 (水) 00:00:00 +0900 (JST)
It's in the Year, Month, Day format. So, the dates match. That means this is the right version.
Applying the Patch:
Extract the archive. Copy the adult.rpa file into the game/ folder. Launch Highway Blossoms.
Activating R18+ Content:
Go to General settings and enable R18+ Content.