The first thing you will need to do is click "Create gallery" and give your gallery a name. You can also enter some descriptive text of what pictures are in it and choose whether users can comment on pictures and whether to show the most recently posted pictures at the start or the end. Once you're done, click "Save". This is the same screen you see if you click in "Edit settings" for an existing gallery.

Once you have a gallery, click on its name to see the pictures in it. At the bottom of the page is a link to upload pictures; choose some files here and enter some captions for the pictures, then click "Upload". Once the pictures are online, you can use the << and >> links to reorder then, the X to delete them or click on the "Caption" link to edit the captions. If you change any captions, you must click on the "Save" button which appears to save your changes.