From what I understand and from what I saw from watching videos about the feature, you can basically add your meds umanually, as in entering all the details by yourself, or scanning the label on the medication using the camera.
If you decide to fill in the details manually, then you'll get an search box where you can type the name of the medication and see the search results so you can pick the one you're using.
After then you pick the strength etc.
I'm having a problem with using the feature with voiceover, I can't seem to be able to find the button for scanning the label with the camera, and also the search box doesn't behave like one.
I can only type the name and it doesn't show me any results or anything really.
Also the weird thing is that I can't find the IU unit from the medication strength units.
I'm not sure if what I explained above is a bug with Voiceover, or it's simply one of those things that didn't make it to the first release of iOS 16, but I saw a youtube video talking about the feature saying that there is a search box you type in the name there and you can pick the one you want from the results. They have also showed scanning the label using the camera.