Fashion Design

Visual merchandising is something related to retail industry which helps in boosting sales of a retail store.
As you have completed class 12th in 2016, I assume now you are pursuing some Diploma or graduation. For a visual merchandiser, two things are required; 1) Knowledge of design 2) Knowledge of sales.
You can have these options to enter the retail industry: - completing a retail design qualification at college while looking for work OR moving from an in-store sales assistant role to a trainee visual merchandiser post.
Pursue MBA in marketing and join as an in-store sales manager and then shift to trainee visual merchandiser, this way will help you gain knowledge of sales as well as visual designing. If you go for a course then acquiring sales knowledge will be a little difficult task.
Hope I have added some clarity to your thoughts.