It's simple to import photos from your iOS device's Photo Library.
For Notes:
Use the "Image" note and pick "Photo Library"
If it's the first time that you'll be using it, it will ask you to allow the app to load your images. Allow it.
You'll now be able to import images that you have
Records:
Create a new Health Record
Add the details, then tap on "Add Photos" and select "Photo Library"
You'll now be able to import multiple photos at the same time.