If you view the issue, there should be a button at the bottom that says, "Edit this Issue".
As for creating a title for an OGN - it's necessary for two reasons - one technical and one content-based.
The technical reason is that the site is predicated on every issue having a title to be associated with. Without that title, the issue would be unable to be rooted in the system (for lack of a better description).
The content reason is that while the OGN may be intended to be a one-shot, it is not inconceivable that a sequel could be made, even years down the line. They shouldn't be seperate if they're both from the same title.
As a rule, it's better to keep everything consistent