Just go to the Election Results map. Find the state you want to make a county map off and either Ctrl+C the page or use Light Shot (
https://app.prntscr.com/en/index.html) to screenshot the county map. After you have done that go onto a editing program like Paint.net or MS Paint and fill in the map the way you want. Then after you have done that save the picture, go into the gallery section, find where you want to put the map and then click add image and paste the image file you made into the gallery. Then there should be a use map in forum link which gives you a link which you can use to use it in the forums.