Where can I find my attestation of achievement?

You can find your certificate of successful completion on your dashboard (here), in the "My certificates" section and then on the "Attestations of achievement" tab:

You must have obtained the minimum score indicated on the progress graph (see How do I read my progress graph?).

Certificates are generated on a massive scale by FUN after the assessment period. The teaching team will let you know by email and/or via the "Course Info" tab when they have been generated.