In order to obtain a work visa, you will first need to secure a job. The reason for this is that the visa application is based on a specific job and the employer acts as the worker's sponsor. The employer will usually handle the application, but you will need to submit certain documents and go for a medical test. Click here for some more details on the process. Once you have your work visa, you will also need to apply for a residence permit.
For tips on how to find a job, please see this page.
Best of luck.