You have to write a story in 4 minutes after seeing a picture for 30 seconds. It is to assess your intelligence and ability to observe in a short span of time and the write a relevant story. I think you will be given 60 seconds to note the details. Then the 4 minutes start in SSB PPDT(picture perception and description test) assessment.
1.In that precious time you have to practice in sign language/short form about writing the key details in the picture.
2.For instance if its a related to a train station or prayer hall or hospital or an vent robbery, assault, playing or borrowing a book in the library.So you have to quickly learn to capture the essence of the scene and
3.Then move on to the key players. a building, a bed, a tower, a tree etc, then the peopel - child, male,female, officer,farmer etc.
4.Then the expressions or the mood, a sad beggar, a joyful child, a threatening robber a sacred lady.
5.Lastly try to link the characters, the mood, the background and the essence of the picture. Eg: a beggar begging in front of a temple, a young man running to catch a moving train, a lady in fear because a thief is trying to rob her in the street or in the house.
6.Be sure to write down the position of the character and encircle the main character.
The your 4 minutes start. Here try to limit you story to around hundred to hundred and fifty words.
Formulate basic sentences that are meaningful yet do not have too many words.(It was such a wonderful, pleasant,lovely sunny day should be concise as It was a pleasant sunny day). The sentences will be based on the above 4-6 observations you have made. Do not try to have a flowery language with many adjectives. Keep the language simple.
This needs practice,practice and only practice. What you can do is, there are many websites that have online resources. Carefully see the image and the replies given for them, you will get an idea of the type of response that you can give.
Then time yourself as if you are in the exam and see your performance. I suggest you see a picture and try to get the details in a card or a empty rectangle in 60 seconds. Do this many times and once you do many such picture cards, you'll get the idea how not to miss details, The start practicing to write 5 sentences first about a picture. then gradually increase the content in the same 4 minutes time.
For example a picture of a fireman on a tall ladder rescuing a woman from a III floor building on fire with the rest using water jets to douse the fire.
If you can get all these key details in 60 seconds, then well done. Move on to improve your story writing
Hema was trapped in a fire. The firemen came quickly and sprayed water. Mohan, a brave fireman went in and brought back Hema safely.
Now try to improvise by adding details.
Hema lived in the III floor of a high rise building. One day fire suddenly broke down and she was trapped in the III floor. Luckily she had the presence of mind to call the fire service. The fire engine promptly arrived and water jets were immediately used from multiple sides. Mohan, a brave fireman saw the plight of Hema and quickly swung the tall collapsible ladder to extend up to the III floor. He jumped in and quickly picked up her and safely came down the ladder. Thank God for the timely help, Hema is alive today.
This is just an example. It will take time for you, Don't worry keep practicing.
You can get online resources from such sites. All the best