Blender creating amateur tutorial

Below is the tutorial I am following

Summary
1. Create an Amateur bone
2. In the bone property , tick X-RAY so you can see it inside the body
3. On edit mode, press the tip of the bone and press E to extrude a bone for the monkey head
4. On edit mode, press the tip of the bone, tick the "X-mirror" on left hand side and "SHIFT-E' to extrude two arm bone for the monkey
5. select the arm bone , press "ALT-P" to disconnect it from the parent, drag it to the arm
6. To do the leg, "SHITF-E" to extrude then 'ALT-P' to disconnect , 'G' to move it to the leg , 'R' to rotate, 'S' to resize
7. make sure all bone "ROLL " set to zero
8. on POSE MODE, add BONE constraint -> inverse kinematic-> chain length 2 to both lower leg and lower arm
9. on object mode, select your monkey mesh, APPLY-> ROTATION AND SCALE
10. Finally , "SHIFT select MESH and AMATEUR" then "CONTROL P" set to automatic weight