You have to find the schematic, and read it. That will unlock the crafting. Name of the schematic is "Vehicle Plow Mod Schematic" in the English version of the game. It is not something you can unlock just by leveling vehicles crafting skill up.
All schematics are randomly found. However, you have increased chances to find them in POI that have more book/magazine drop locations, such as Crack A Book. The odds for each container aren't higher, but more containers mean more chances. Like some other vehicle mod schematics (supercharger, for example), it isn't a common drop and it can take a while to find it unless RNG smiles on you.
As a note, there *may* be certain containers that have a higher chance of that mod dropping, but I haven't looked at the loot tables. If there are, they would likely be the Pass N Gas crates. And if so, you find those more often in garages.