Open the Fabric or Forge installer you downloaded and click "Install".

Open your Minecraft launcher, go to "Installations," and click the folder icon next to your modded profile. This opens the .minecraft directory.

Filter by your Minecraft version (e.g., 1.21.1) and loader (Fabric or Forge).

Once in-game, type //wand in the chat. If a wooden axe appears in your hand, WorldEdit is working. How To Download & Install World Edit 1.21

Click the three dots or the download icon to save the .jar file to your desktop.