Writing comic books is a skill that comes with lots of practice and in most cases education. While you don’t necessarily need to have a college degree to write a comic book, you do need to have creative writing skills to develop a plot and character traits of the characters in the story. It is not a simple matter of writing a description of what is happening in the picture because there is really no need to do that. The picture already tells you what action is taking place. You have to develop the speech that will keep the story flowing, add the thoughts of the characters and put in the connectors from one scene to the next.
Writing comic books is very demanding and challenging work. The writing ahs to be done before the pictures are created- not the other way around. This means you have to have detailed writing that will help the artist to interpret the story. It is not the same as writing a book or a story because you have to speak directly to the reader and them hand your work over to an artist who may or may not present the story line exactly as you had anticipated.
When you are writing comic books, you don't have to add the words that describe the action. This is the job of the artist, who also has to express emotion in the faces of the characters, so you don't have to include how they feel in your writing. You have to excite the reader with your words and spur the artist to portray your message through the images on the page. Therefore you do need to write instructions, such as 'Tom is angry in this scene.'
There are two methods you can use for writing comic books. One of these is to write the full text so that you have full control over the whole process. You write the story, describe what is happening in each scene and how you want the character portrayed. Another method is to write a basic synopsis of the plot with descriptions of the characters and the setting. The artist takes this and creates the images and then you add the dialogue.