From The Document Foundation Wiki
- Browse to directory containing the drawing files you want to add to your theme and then click .
- Click in the combo box File Type to limit to a kind of file, and accept to update file list with Yes.
- Select files you want to add:
- click to install all files contained in the list,
- or Ctrl+Click on specific files you want to add, and then validate with button.
- Click when you have done.