Which layouts are you trying to import? The Standard layouts are already included in the install of Sculptor. If you want to import ems based layouts, you should unzip the file downloaded from the site. Then select the .xml files that are directly within the directory you just unzipped. The name will look something like this:
or something to that nature. In the same level directory, there should be a directory that has a corresponding name. Do not select to import anything from within that directory.