new chickens; locked up or let out?

Hello everyone! finally got my 3 girls and their house today.  been reading about it for ages and took the plunge this morning.
I have a question though, they have their house and a fenced off area of the garden. hubby and i have just put them to bed but am i meant to keep them locked in there for a day or two or are they ok wandering the garden?
Also their bit of garden is the weedy bit but should i put something down (wood chips?) as well?
all help welcome to make their life (and mine!!) very happy!
 

Just open the door in the morning and they'll come out when they are ready.

Weeds!  YUM!  They won't last long.  Our pen is now bare earth, and it's perfect for digging and dust bathing.  I only use woodchip if it gets too muddy.