How to make solid trees?

Can anyone help me, I am having issues with trees. Whenever I paint trees in the terrain tree painter I can pass through them, I have read every possible answer on how to solve this issue but I am still getting nowhere with it. When an answer says to create a new prefab with a capsule collider then use the paint tool with that tree I do just that but instead of having a solid tree, I don’t get a tree appear at all. Please can anyone help?

80820-terrain-trees-101.jpg

This should help you.