How to use the cannon.Body function in cannon

init() {
    /*----- CREATE WALL -----*/
    const wallBody = new CANNON.Body({ mass: 0 });
    wallBody.addShape(this.fixedCubeShape);
    const wallMesh = new THREE.Mesh(this.fixedCubeGeometry, this.material);

    /*----- SET SPAWN POSITION -----*/
    wallMesh.position.set(this.x, this.y, this.z);
    wallBody.position.set(this.x, this.y, this.z);

    scene.add(wallMesh);
    world.add(wallBody);

    this.wallMesh = wallMesh;
    this.wallBody = wallBody;
  }
}

init() {
    /*----- CREATE FIXED CUBE -----*/
    const fixedCubeBody = new CANNON.Body({ mass: 0 });
    fixedCubeBody.addShape(this.fixedCubeShape);
    const fixedCubeMesh = new THREE.Mesh(this.fixedCubeGeometry, this.material);

    /*----- SETS SPAWN POSITION -----*/
    fixedCubeMesh.position.set(this.x, this.y, this.z);
    fixedCubeBody.position.set(fixedCubeMesh.position.x, fixedCubeMesh.position.y, fixedCubeMesh.position.z);

    scene.add(fixedCubeMesh);
    world.add(fixedCubeBody);

    this.fixedCubeMesh = fixedCubeMesh;
    this.fixedCubeBody = fixedCubeBody;
  }
}

init() {
    /*----- CREATE PLAYER -----*/
    const cubeBox = new CANNON.Body({ mass: 0 });
    cubeBox.addShape(this.fixedCubeShape)
    const cubeMesh = new THREE.Mesh(this.fixedCubeGeometry, this.material);

    /*----- SETS SPAWN POSITION -----*/
    cubeMesh.position.set(this.x, this.y, this.z);
    cubeBox.position.set(cubeMesh.position.x, cubeMesh.position.y, cubeMesh.position.z);

    scene.add(cubeMesh)
    world.add(cubeBox)

    this.cubeMesh = cubeMesh;
    this.cubeBox = cubeBox;
  }