If you see a project that suits your skills, click on the 'Apply to this project' button to apply.
Fill in the Budget, Time Estimation, Language Pair, and Notes for Client.
Be sure to write a good explanation of your qualifications in the notes, this will help the requester evaluate if they want to choose you for this project.
The better you explain your qualifications the more likely the client will be to choose you for the project.
After that you must wait for the requester to accept your application, please see the application flow article for more details.