How do I edit the event invitation

I'll show you an example on desktop.

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1. ​On your home page at https://app.celebrate.buzz, tap the Celebration you want to edit
2. ​Once you've done that, tap the Edit icon in your sidebar
3. On the Edit page, tap Edit event details, and walk through the wizard. One of the steps is the invitation page. You can now edit it. Once saved, it will immediately be live.

Here's a screen grab from the Desktop view