Manipulate[GraphicsGrid[{
{Plot[LegendreP[l,m,x],{x,-1,1},ImageSize->375]},
{Plot[LegendreP[l,m,Cos[θ]],{θ,0,2π},PlotRange->{{0,2π},All},Ticks->{ Range[0,2π,(π/4)],Automatic}]},
{PolarPlot[LegendreP[l,m,Cos[θ]],{θ,0,2π}]}}],
{{l,2},0,20,1,Appearance->"Labeled"},
{{m,0},-l,l,1,Appearance->"Labeled"},
ControlPlacement->Left,
SaveDefinitions->True]

Manipulate[
LegendreP[l,m,Cos[θ]],
{{l,2},0,20,1,Appearance->"Labeled"},
{{m,0},-l,l,1,Appearance->"Labeled"}
]