Hello, Welcome to the Forums.
If it’s a publicly available tutorial, can you please share it? I’m curious to see if they are using their own imported meshes or Fornite meshes.
I just did a quick test and was able to add my own static mesh to the foliage painter, but was unable to add any Fornite meshes. (Probably because they are wrapped up in ‘FortPlaysetPropItemDefinition’ classes)