Planet Building?

Hi everyone, I am trying to start a new project and I need help for where to start.

I am basically trying to make the moon titan in unreal engine. I dont know how to build the initial planet. This is the area I need the most help. I used the voxel plugin to start off with but it always fail to create the intial planet. I dont want to have to buy anything for the market place. Is there something anyone can with?

I have the textures and all the assets I want to use.

I want to hand place all the assets