Question: how to modify includepath in a worksheet and an mpl file?

Let's say I have an mpl file and in this file there are several lines $include<~/~/~.mpl> and in some of those called mpl files, there are also some more include lines. And assume the paths of these files are given relative to a specific folder. Now I guess this specific folder has to be mentioned by modifying includepath. But looking at the help pages related to includepath (here and here) I get this sentence "it can be modified by calling kernelopts(includepath)", but I tired typing things like kernelopts(includepath):="C:\\Homes\\testFolder"; and still I see "" for kernelopts(includepath);. How can I tell Maple to look for the files relative to this location either by typing something at the Maple worksheet before typing read("C:\\Home\\testFolder\\main.mpl); or by adding a line at my main mpl file?