Ah, sorry. I assumed it was part of the app.
How do you intend to use the image? By that I mean there’s an Image component for the forms which will allow you to upload if it’s going to be part of the form layout.
But if you want to upload an image for use by custom HTML, you can also go to the “Assets” under “Theme” in the app browser on the IDE :
If you click that choose “upload file” in the “choose an asset to edit” drop down :
you can then reference the resulting file like so (for example) :
<img src="_/theme/imagefilename.jpg" />
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