Fetal doppler.....where do i position it to pick up heartbeat at 10wks pregnant??

Hi have just bought a bestman 500 which can be used from 10wks and I am 10+4. Now I KNOW the heartbeat can be hidden and I KNOW we may not pick it up till wk 12 but Id like to know where is the best position to pick the heartbeat up??

Apparently its lower than you`d think?? Is it the pubic bone or just below bellybutton?? Is it usually central?? Thank you in advance