A publication consists of a number or issues. There are no limit the the number of issues for a particular publication.
Issues are ordered by the issue date, the most recent issue (the one with the latest date) will be the shown first.
To re-order the way issues are displayed, change the dates of the issues into the order you want them to display.
Issues will not display on the URL you chose, or in the 'Browse Issues' panel, unless they are marked 'live'.
You can change the status and other things about your issues using the 'Edit Issue' button.