First, get a command block by saying /give @p command_block or minecraft:command_block then get a red stone device, If the video does a red stone block, use that. Do the command away from land. It can grief. Find the command on the Internet, Copy it, and press Control + V in the command block. Then press done, and put red stone device next to it There are special commands, Custom game mode commands, furniture, or heads. Always ask a admin. If you forget, just read this. Commands can be dangerous, they can grief, or even crash the server. Or mess up a city, like Los Vice in Version 2. A Operator is to use the commands with honor.