Hello. I downloaded the MX-Trackmania Sign Pack zip file and extracted the MX file inside to the "MX" folder inside into my Documents\ManiaPlanet\Skins\Any\Advertisement folder. Then opened Map Editor and NO signs. I'm just looking for some signs that are bigger and good looking to put in my maps, like animated arrows that are actually visible from a distance (you know like the ones that are in the Canyon maps that I play online). The Signs that are on ManiaPark are few and small. Any help, please?

Based on your description, it looks like you did everything correctly. Did you have ManiaPlanet open when you added the signs to the folder? I believe ManiaPlanet needs to be restarted before any new signs appear.