How to create my own tree?

Hello. I created my tree model in Blender and imported it. But I don’t understand how to turn it into a tree. I made a 3D Object - Tree, put my mesh, but I couldn’t put the leaves and got confused. Help me please.
Thank you.

The Tree object is not meant to be used with models from other 3D applications, instead you can use the Tree Editor to create the tree directly in Unity: Unity - Manual: Tree Editor (unity3d.com)

If you want to distribute your tree model on a terrain, you can add it in the “Paint Trees” tab of the terrain. However, it won’t react to wind zones in this case and you won’t have automatic LOD.