/layer/ is an experimental board for desudesutalk, usually shortened to DDT. DDT is a userscript which allows arbitrary text to be embedded in images. As such, text is not allowed on /layer/.
To use DDT, you need Greasemonkey, also known as Tampermonkey on Chromium and Violentmonkey on Opera. Once that's installed, use this link to install the script:
https://github.com/desudesutalk/desudesutalk/raw/master/ddt.user.jsRefresh the page and get your keys set up by clicking the icon in the bottom-right. Click "log in" and enter any password and number you choose, and keep them both secret. Write these down somewhere. Wait a while as the javascript runs to generate the resulting key. This is your public key.
To make sure everything works, navigate to a thread and head over to the "messages" tab. Click "get old messages" and the script will attempt to decode messages in the thread. You will probably not have anybody sending messages you can see at first. When you write a message, it is signed in such a way that only people in your contacts can see it. If you have just generated a key, nobody has you in your contacts, and you will not be able to see messages.
You can add a public key to your contacts and give that person a name by clicking the "add" button under an image they have posted. Once you have some people in your contacts, you can start posting messages to them.
That's the basics. A slightly more detailed guide can be found on Github at
https://github.com/desudesutalk/desudesutalk/wiki/How-to-use-this-script , but aware it is somewhat difficult to read.
