Breath out as you fold forward from the hip taking the hands to the floor.
If your hands won't reach the floor with straight legs then either bend the knees or hold onto the shins.
The most important thing is to bend at the hips rather than arching the spine. You should feel the stretch in the back of the legs.
Try to rotate the hips so that the sitting bones extend skywards.
Notes
An upward forward fold could be included at this point.