Hey there! So documentation is still from the beta program. But there are some nuances to the workflow you can find in the article. Read everything twice in that article.
Like the folders they reference are different in beta than they are now /Metahumantest/ is now /Metahuman/. See how my reference to the calibration board is /Metahuman/ now.
Stereo Camera Calibration and Tools | Epic Developer Community (epicgames.com)
Condense it to the simplest of terms.
you need a calibration board which is located here.
C:\Program Files\Epic Games\UE_5.2\Engine\Plugins\Marketplace\MetaHuman\Content\StereoCaptureTools
Once you have the calibration video and files you should be able to follow the articles to break down the videos into imagesequence json folder. From there you can bring it into capture source because it sees that JSON file. Hope that helps.
GL