If you are trying to Edit any of your past campaigns, and you do not see an "Edit" option, please check the "Status" Column first. If the status reflects "Archived", then that campaign can no longer be edited.
You can Edit only "Active" campaigns, once a campaign is over and 30 days have passed Let's Calendar automatically archives this campaign. In case you want to create a new campaign on similar lines, please press the "Duplicate" campaign button and then you can create a new campaign with all the same parameters, content, descriptions and even users, and set it up in the upcoming calendar.