Foliage Brush won't paint in all meshes

Hi, I’m trying to work with the foliage brush in Unreal 4.13.2, for my foliage I’m using three different packs that were purchased from the marketplace. So far I’ve only gotten one of the packs to work with the brush, when I do the drop down “+Add Foliage Type” only the forest collection pack is available for selection and dragging and dropping meshes in from other packs puts them in, but they won’t paint on the landscape. (Won’t even make the blue, sphere like brush show up) I was wondering if I’m just missing a checkbox or something, or maybe need to move them into another folder?

My second problem is that the trees I have purchased have a base, and when painting them on the landscape it places the base on top of the landscape instead setting it slightly inside. I could paint them all and then offset them so that they sink into the ground, but the only problem with this, is that now all my rocks are underground…so i was curious as to if there was a better, faster way to do this. Like moving the “bottom” of the mesh up a little bit or something.

I’d appreciate any and all help, thank you in advance :^)