You will only be able to contact a freelancer if they apply for your job, or if you invite them to your job. Please post a job so that you can start looking for freelancers that will be good for your project.
@Joe M wrote:
Are you in your client account, as opposed to a freelancer account?
If so, you would see two buttons towards the top right of your screen, one saying "Invite to job" and one saying "Hire Now"
Use the former to contact a freelancer.