To update a resource you need to select the “Templates” page from the top menu bar then click on My resources folder located in the left sidebar. After that, a list with resources will show up depending on your selection(Templates or Stylesheets) . Next step is to select the resource and then you will see the details about the selected resource .In the upper right corner you will have a menu bar :
You have to select “Update” button and a dialog box will show up where you can choose the resource file.
Be aware because the file you’ve selected at the previous step need to have the same file name like before. In case you want to update a resource file with a different name this dialog will appear: