Exporting inDesign IDML file to Apple ibooks author, missing graphics, fonts

I would like to publish my book on Apple Books. Hence I took my Indesign file (rich with graphics and custom fonts) and exported it as a IDML file. I then tried to open it in iBooks Author, the suggested tool for transferring files to the apple iBooks store.

The file after I inserted  into iBooks author as a chapter is missing all my custom fonts as well as all the graphics. The graphics in my InDesign file were all linked and in a separate folder. The graphics in iBooks in the imported chapter are all in blank frames with a quesiton mark. I used the proper import media and graphics option when importing it into he file into iBooks. Does IDML file only save text? The graphics are separate? Do I have to transfer the graphics folder to the Mac separately? Where would it kept for it to link to my IDML file in iBooks?

Also what to do about the fonts? Do I have to preinstall all the fonts on the Mac as well? The font issue, I can sort of understand, but don't know what to do about the missing graphics. Your help most appreciated.

I am using Indesign 2019 (from the CC set.)

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