How can I get a command block?
Press T and then /, or just / to bring up the command, then type /give @p command_block and press the enter key (↵ or Enter).
You will first need to type / to start typing commands, then, after that, type:
/give @p minecraft:command_block
Just for notation, a command block's ID is 137
mc version 1.10:
/give (userid) minecraft:command_block
mc version 1.9 and under:
/give (userid) command_block
To get command blocks in Minecraft, you type /give (Your username) command_block.