Covid Testing in Belgium after returning from the UK

Hi,
I will be arriving in Belgium from London this week via Eurostar. I will complete the Locator form before I depart. The regulations state that I need to quarantine and have a COVID test on day 1 and day 7 in Belgium. Do I receive a test code by Text Message? How much do the tests cost? Where do I need to get the test done? How will I get the test result? So many questions.
Thanks