Thank you for your post.
Applets are written using the Formativ Language, which is an extension of Visual Basic Scripting Edition (VBS). Learning VBS would be a good place to start.
Once you have a grasp of VBS fundamentals, I would suggest you work through the Developers Guide (part of Creator and Studio). The Language Guide is also a good reference.
You can also down many example applets from our downloads page. These are a good source of techniques and ideas.
You need Creator or Studio to write applets. While you could theoretically write them with any text editor, you wouldn’t be able to run them.
I hope this helps.