It is possible to import timesheets to Staff Squared. To do this, navigate to the profile of the staff member you wish to import a timesheet for and open the timesheets tab.
Here you can download template and populate it with your timesheet data. When you're done, save the file and upload it to step 3 of the page you downloaded the template from. Then click upload.
NB: You only need to complete either Start and end time or Duration.