Where does the opportunity cost should go when calculating the NPV of the project?

is that in the CFO or at the beginning of the statement? because I'm not sure where it should be calculate when you calculate the NPV of the project.

meaning if I can open a restaurant on my parking spot and use all the area I'll generate 300 sales, but if I use just half of it I can rent it for 5K per year.

So how do I take into account this opportunity cost when calcuting NPV?