Just select the pictures you want to reduce in a File Browser, right-click on it and choose F-Spot Photo Manager.
The selected pictures will be displayed as a list. Select the photo you want to reduce and choose in the menu bar: Photo -> Export to -> Folder
To specify where to save your pics, choose a folder and a Gallery Name which another folder that will be created and will store reduced pics and choose the option Save the files only in the Export Method.
Finally choose Style and Resize to
