How to add several volumes (cube, cylinder or sphere) in the same object?
Right-click on the cube you created in the previous chapter and choose the menu OBJECT > EDIT MESH ...

then select the CUBE, CYLINDER or SPHERE mode and click on the floor, even several times : volumes appear then there.

To see the drop-down list of all your textures, click on the 1 above the texture image square. You can choose the number of a texture (1, 2, ..) or add a blank one to the list with NEW.

To load a new texture, choose the number from the list (1, 2, ..), then click on the square to take a new texture to your PC.

To apply a texture to a volume, go to APPLY TEXTURE mode, then select the texture from the list (1, ..) and click on one of the small pyramids on the volume. You can also choose one of the sub-options (mesh: to change all volumes, polygon: to change only one face etc)

Always keep the window EDIT MESH open and pull items from your inventory into the world : they will be added to your object.

To pull/stretch these volumes, select the MOVE/STRETCH mode, click on the point of a volume and arrows appear. You can choose :