Hey Laura, you can edit both the series and edition name in HQ.

If you want to edit the series name, select the gear icon on the top nav bar in your series workspace > select "Strategy" > modify the series name under "Series title"

If you want to edit the edition name, I'm assuming you're referring to the subject line. You can select the edition subject line on the drafts page, and edit the subject line in the editor. You can not modify subject lines for sent editions.

Let me know if you have any other questions :)