I am a UX/UI designer and I am new to freelancing. I was reading about how the houly-paid system works and how it sends screenshot of your screen every 10 minutes or so. My job generally involves a lot of thinking and doodling/sketching on paper. So my question is how will the client know that I was working if he/she can't see anything on the screen, atleast for the first part of the job.
That's a good question. So I think the Upwork Tracker allows you to take screenshots from your webcam, so you may want to point your webcam to your desk so that they can see you working.
Though, this won't register any activity on your computer and as a consequence you may not be eligible for the Upwork Hourly Protection (it requires decent levels of activity).
Since the focus of Hourly contracts is to track freelancer's computer activity, you can consider setting up your contracts as Fixed-Price with Milestones. There is an option to add the time manually but Hourly Payment Protection is not available in that case.
You can find more information in the freelancer resources we shared here.