You click on Maplestory and out of frecuancy comes up what do you do

Your monitor can't support the frequency the program is currently trying to use. To fix this, go to the folder you installed maplestory to, most likely Nexon under the C drive. Then double click on the Nexon folder. Search for Setup.exe, which should look like a small mushroom with a face, and double click that. Then just follow the directions it gives you.

Hope this fixes your problem, good luck!