1. Handling blocks
The toolbox (left) will display all blocks in the currently opened collection. Scroll through pages of blocks using the arrow buttons at the bottom. Cycle between the various block collections using the folder icon on top.
Click on a block in the toolbox to select it. Place it in the scene by clicking anywhere on the grid. If you hold shift you can place multiple instances of the same block. Spacebar rotates the block and holding control (command on OSX) will change the grid snap size.
If a block is placed you can select it by clicking. After selecting you can move it around by dragging the arrows, you can scale the block by dragging the cubes around it. If you press H, J or K you can mirror the currently selected block. Pressing delete will remove it.
2. Changing materials
Select the material tab (left) to color blocks. You can create a new material by pressing the plus icon next to the already existing materials in the scene. Change the color of a material using the color picker and change the texture in the texture tab. By selecting a material and clicking a block you'll paint it.
Press save to save the project file to disk, you can open it up later using the load button in the top bar.
3a. 2D sprite
Click the "2D sprite" button in the top bar to render a 2D sprite of the current open model. There you'll find options to change the camera position, filters, shadows and even batch processing to export different angles and levels.
3b. 3D model
Click the "3D model" button in the top bar to save the 3D model to your disk. You can choose between either OBJ or FBX file format, depending on what your game engine of choice supports. By merging the model you won't be able to directly manipulate separate blocks in the final format, although it's better performance wise.