In MyChart → Menu → Document Center (or Sharing → "Download My Record").
Choose Continuity of Care Document (CCD) and save the .xml file (or .zip — extract the .xml).
In MyBloodTest → Sync tab → Import Data → pick the .xml file.
Every lab with a LOINC code is imported with its value, unit, reference range, and date.
Works on iOS, Android, and web. Any portal exporting HL7 C-CDA — Cerner, Athena, Meditech — works too.