Creatives are using their application to sell themselves and their work to you so the more specific you can be within your brief as to your requirements the greater the ability of the creative to establish whether it's a project for them.

A creative will apply with existing examples of their work which fits the style you are looking for, they will explain about themselves and their work history as well as video and image links - you can also link through to their profile which will include examples of their wider work as well as their social links. 

What you are looking to see from an application is the creative demonstrating why they are suitable for the project and confirming this with relevant examples of their work.