The key thing is open and image, apply effects etc and then you can either go to the standard file save etc commands or you can go to the top left and select the export persona. Entering that you will find you have a limited set of panels as well as tools but they are perfect for the generation of files in multiple formats etc. You can create a slice from an existing layer, you can create slices using the tool panel. You can also re-size them and all can be controlled via the panel and for each of those, you can set up a single or multiple file save to a number of formats such as PNG, TIFF, SVG etc and you can do that by command or just setting up the continuous and you will see any change reflected in the external files.
Open an image and go the persona, once there the panels will change and you will see layers and slices etc. Go to the slice tool and create one and set it over something in the image that you want to resize. You can repeat and create multiple entries in the slices panel. You can go to that panel and expand out the entries and set the file to be created to be PNG or JPG etc and also you can set a size such as 5 times the current size, 20 x the current size etc as well as other settings. It will create a name for the file. Now go the bottom right of the panel and click the button and you will be asked for a folder for the files or you can cancel. You now have a set of PNG files that are 20 times the size of the original part of the image selected creating a wonderful blow up image.
There are also a lot of presets for the files in the slices panel such as retina PNG, Apple universal icons, OSX application icons and so on.