You can start by creating your Upwork profile. Here's a link to give you some pointers on how to go about it.
Keep in mind that like you, there are a lot of freelancers looking for jobs too in Upwork. That's why it is always best that when building your reputation and Upwork profile is to take more skills test and certifications, adding more value to you. Start with a low rate as you build your Upwork profile and look for jobs/task that are within your skills of expertise.
And when you do get hired, make sure you provide an excelent performance. Employers would rate your performance and this would increase your chances of getting hired or re-hired.