Once you finish with that part, go to the "File" tab, and find where it says browser storage. This is a progress saver and will store the current version of the work in the kleki browser so it will be ready next time you get to it. Click the "Store" button to save it to the browser.
However, things can happen so every time you save, save it both as a PNG and a PSD. To do this, find the "Save" button. Click it to save your png. Then find the dropdown menu next to that button. click it and switch the format to "PSD" and then save. The PSD will help prevent your work loss. When you upload a PSD file, all your work is uploaded with your layers intact and ready.