Yes, Kei! The purpose of the website it to connect freelancers who have specific skills and experience to clients who have jobs and projects in specific niche markets. You should be able to look for clients in your specific job category (sound designer), apply to their job posts, and work on the job through a contract through Upwork.
For help getting started, please read up on the freelancer resources for great tips and insights on how you can work successfully on the platform.
For more information about working safely through Upwork, please read these tips for avoiding questionable jobs.