To edit your listing on SidelineSwap:
From desktop web: Hover over the listing and click the pencil icon from the locker view or the pencil above the listing from the item view.
From mobile web: Click the pencil icon below the listing from the locker view or the pencil above the listing from the item view
From the App: Click the pencil icon below the listing from the locker or the three dots at the top right of the listing from the item view.