When to follow up after Interview?

I had an interview last Tuesday at 4 PM. This was the second and final round. When should I follow up?

When I had my phone interview, they called me 3 days after to schedule the in person interview.

Also, what should I write in the email? It Will be going to HR as I don't have the hiring manager email address ( I sent a thank you email to hr after my interview to forward to the hiring manager I had met with)