Use the mouse to move the block, and click to place. Press "e" to open the inventory and click the arrow button to scroll through. Click on the block you want or press "e" again to exit. Press "o" to activate eraser. Press "a" when you finish building. If you aren't building in the Nether or the End, press "q" to change the weather.
New features: All new starter worlds: 20 easy-to-load, simple worlds to give your design a boost! Improved design of 87 blocks! Most changes were minor, but some of the older blocks were completely overhauled. 94 Brand New Blocks, including a bunch of new banners, beds, and stone bricks! Credit to Minecraft, and myself.