We bought the tests at emed.com. If using this for a return test, looks like you need the app and the test "registered" before you leave the US. emed sent me this note:

"In order to receive a test result, digital lab report and/or health pass after participating in a virtually guided test session with an eMed Certified Guide, an individual must have registered and downloaded the NAVICA™ app while inside the U.S. and its territories and a Binax NOW Home test Kit."