Hi,
the section "Spells" only offers maps with some (sometimes only one) triggered spell(s). When you want to use those spells, you have to create an ability similar to the downloaded map and to copy and paste the triggers into your map. Then you just have to replace the ability in the new triggers with your ability to make the whole thing work. Usually you don't download new models by downloading such a "spell-" map, they're just already given effects or models of Warcraft3. Sometimes the triggers in some downloaded maps also include regions, which you have to replace with your own regions.
I hope I was able to help you, if not, just ask again.
-greetings, Pajam