Select the AUGMENT tab

Then click on theto select JavaScript or JavaScript Block from Template

Let's start from scratch and select 'JavaScript'


On the New Block form, under the Basic tab, give your block a Name, a Version number and if you have one upload an icon (512 x 512).

In this example we named our block 'Hello World JS Block'

You are ready to go to Create Block and Go to code (bottom of the screen)

Learn more: JavaScript Editor