Every time users want to interact with an inserted Content Add-in in Excel / PowerPoint for iPad they first have to double tap the Content Add-in when you shouldn't even need to single tap to focus it first. For some reason, only on iPad, single tapping anywhere on a content add-in results in showing the long-tap context menu (with Cut, Copy, Delete, Edit Add-in options) instead of immediately interacting with it (eg. performing a tap on the button or UI element inside the content add-in you just tapped on, without even needing to single tap to focus it first). And strangely long-tapping the content add-in does nothing at all, instead of showing that context menu as expected.

Instead, just like on PC, web etc. platforms, tapping the edge or corner of the content add-in should show the grips for moving/resizing it. You can even if preferred show the context menu (Cut, Copy, Delete) at that point too, as well as show again any time you long tap on the content add-in while in the move/resize mode.

Though doing that should IMO be sufficient, if you really thought it needed to be even more obvious, you could always show a small grip at one corner of the add-in (similar to the arrow shown when focusing on content add-ins in Excel for PC, but much smaller) which when clicked will show context menu and/or immediately enter into resize mode. And/or you could add a "Move Add-ins" toggle button in the Ribbon bar to change click. Or you could even have a long-tap menu shown with Move/Resize option only if/when long tapping an add-in that is not already focused, instead of performing that long-tap inside the content add-in itself, though I wouldn't suggest that. However, IMO those are not needed.

Even simply describing interacting with content add-ins as "Edit Add-in" is confusing – as is done now in the context menu and in the ugly instructions shown on top of content add-ins every time they get focused – since Moving, Resizing, Deleting or Copying a Content add-in is what I would call "Editing the add-in" whereas it makes no sense to require you to "Edit an Add-in" in order to click the pause/play button in an embedded video or to click on a part of an embedded chart or use an embedded data entry form.