While most clients have a stellar experience using their FreeUp account to monitor the freelancers they've hired, the software does not have a screenshot software.
It is a software project that is currently being researched with plans to implement it over the next year.
For clients who highly value screen shot software, we highly recommend using TimeDoctor at a low monthly rate.
You can view their plans here: https://www.timedoctor.com/pricing_plans.html.
You can ask freelancers on the marketplace directly to use this software and they can just send an adjustment to FreeUp's timeclock afterwards.
Hope that this helps!