I've tried to explain to them, using a comparison to education, how the system works. Electoral votes are like a GPA, a summary of the results from all classes taken. Popular votes are like the individual grades within specific classes. The individual grades for (fill in the blank) class determine the final grade for that class only and are totally unrelated to individual grades for (another fill in the blank) class. When all classes are completed, the grades are used to determine GPA.
In the States where Trump received electoral votes, he won the popular vote for that State. In the States where Clinton won the popular vote, she won the electoral votes. Maine and Nebraska are an exception because they, because they can, divide their votes by congressional district.
When it comes to the current system, popular votes do count just like individual grades but they count only for the individual States. In reality, using the education comparison, we have 51 separate elections (classes) for which the popular votes (individual grades) apply only to what happens within that class (state). The popular votes in State (fill in the blank) have nothing to do with the popular votes in the other 50 elections.