This electric eraser and Its instructions are from Chinese origin. So, detailed instructions will be left bellow:
Unpack your electric eraser
(how to exchange your eraser tips) you will see that there is already a thick eraser placed in the electric eraser pen, it is held in by the metal piece that also sticks out of the eraser pen, you will find two similar plastic pieces that you can use in place of the metal piece so that you can insert thin Erasers.
(how to insert batteries) As seen above, you will need 2 AAA batteries, remove the top of the Eraser pen and insert the 2 AAA batteries with the positive side facing up, then reattach the lid.
Enjoy your new eraser
This product is sensitive, so don't press too hard on the paper as it will not work as well. Use light strokes for small scale erasing, as that will be what is most effective.
