Inside Plot Area

p.legend.location = 'bottom_left'

Outside Plot Area

from bokeh.models import Legend
r1 = p2.asterisk(np.array([1,2,3]), np.array([3,2,1])
r2 = p2.line([1,2,3,4], [3,4,5,6])
legend = Legend(items=[("One" ,[p1, r1]),("Two",[r2])],

                    location=(0, -30))
p.add_layout(legend, 'right')