How to load a file during runtime? (Resources folder doesn't work)

Hey guys, I have been trying to solve this for quite a while now, but I can’t figure it out. I am creating an editor for a game and I want to allow designer to make new spells. I need to be able to laod a file during runtime from a folder. I know that Unity has Resources folder for that. But it only works if I put the object file to the Resources folder through Unity. I need to be able to put a file into the Resources folder outside of Unity (just through the file system). Is there any way to do that? The code for Resources file is :

  public void LoadParticle(string name)
     {
         GameObject myParticle;
         myParticle = (GameObject)Resources.Load(texturePath + "/" + name, typeof(GameObject));
         if (myParticle == null)
         {
             print("Cant find particle");
             cont = false;
         }
         else
         {
             particle = myParticle;
             cont = true;
         }
     } (cont is just a variable that I use to determine if I should keep creating a new spell or not)

What I am trying to achieve is that a designer will download a Unity particle system, save it on the computer and will give the game full path to it. Then the game should load the object and use it as a particle for a new spell.

I also tried it with Asset Bundles, but I don’t know how to use Asset Bundles when I only want to download the file from the computer (local file system) not from the server. Asset bundles work perfectly in Debug but not when I build and run it (It tries to connect to some server instead). Thank you so much