In this video, I teach you exactly how you can install World Edit in single player in Minecraft 1.7.10. If this video helped you out, give it a thumbs up. The MultiMC instructions are recommended for single-player. Then, download WorldEdit from the CurseForge site. Make sure you get the right WorldEdit download for your Minecraft version and platform (Forge builds are also there - make sure you grab the right one). On Minecraft 1.14.x versions, you will also need to install the Fabric API mod.
WorldEdit 6.1.10 (For MC 1.12.2)
Changelog
This is a small update to the previously released 6.1.10(-SNAPSHOT) version containing two small but important changes:
* Fixed tile entity not being updated on blocks of the same type (e.g. pasting a chest onto an existing chest wouldn't paste the contents of the chest).
* Allowed edits above y = 255, for worlds with extended height limits (eg cubic chunks).
Minecraft Single Player Worldedit
This mod requires Minecraft Forge and Java 8. There are no other dependencies.
Quick tutorial: Once you download and install WorldEdit, enter a creative world and type //wand. Left click one block, right click a different one, and then type //set glass. You can learn more on the docs.
WorldEdit 7.2.2 (Forge For MC 1.16.3/1.16.
(note: WorldEdit 6 is no longer supported and the documentation refers to some many new specifics of WorldEdit 7, but generally usage will be the same.)