I created a new simulation project called 'Bed Frame':
Im building my fiance a bed frame
More of my public projects can be found here.
In order to mesh your geometry with tetrahedral elements you need to upload a geometry with solids and composed of faces, not only a shell. Try to re-upload the geometry in .step or .stp format. You can have a look at [this] (Can a tetrahedral mesh be created using geometry with only shells/faces?) forum post for more info.
You can than follow [this] (https://simscale-2.wistia.com/medias/1rceuszi3e) video tutorial to create a mesh. First try to create mesh with 2- Coarse refinement level.