About Khan Academy certification

Hi there - My child is going in 5th Grade school now, and he does a lot of practice round the year in Khan Academy Maths. He just loves to do Khan Academy Maths. My first question is, how shall I enroll him for started achieving or completing Khan Academy certifications? And, what are the processes we need to follow for him to enroll & achieve the certifications for KA? I need to understand the complete enrollment process here. Please help.

Second question is, if he started achieving/completing the certifications, how those will help him in his student career further? I mean, we need to understand, how these certificates will provide "values" from top-ranked universities/colleges during his university selection or interview process.