# How to add legend with specific values and frame

I need to add well-defined ticks in this range Ticks -> {Range[0, Pi, Pi/6], Automatic} to the following plot

This is the code but it is incomplete. Comments and suggestion to solve it

Plot[{  1/2 (1 + Cos[x]^2), Sin[x]^2/(1 + Cos[x]^2) ,
1/2 (1 + Cos[x]^2) BesselJ[0, Sin[Pi/3] x]^2,
Sin[x]^2/(1 + Cos[x]^2) BesselJ[0, Sin[Pi/3] x]^2}, {x, 0, Pi},
Ticks -> {Range[0, Pi, Pi/6], Automatic},  PlotLegends -> Placed[{Subscript[(Subscript[\[Sigma], s]), PW],  Subscript[\[CapitalPi], PW](\[Theta]), Subscript[(Subscript[\[Sigma], s]), BB],
Subscript[\[CapitalPi], BB](\[Theta])}, {0.86, 0.5}]]


Use the options Frame and FrameTicks in Plot and the option LegendFunction -> Framed in LineLegend:

Plot[{1/2 (1 + Cos[x]^2), Sin[x]^2/(1 + Cos[x]^2),
1/2 (1 + Cos[x]^2) BesselJ[0, Sin[Pi/3] x]^2,
Sin[x]^2/(1 + Cos[x]^2) BesselJ[0, Sin[Pi/3] x]^2}, {x, 0, Pi},
Frame -> True,
FrameTicks -> {{Automatic, Automatic}, {Range[0, Pi, Pi/6], Automatic}},
PlotLegends -> Placed[LineLegend[{Subscript[(Subscript[σ, s]), PW],
TraditionalForm@Subscript[Π, PW][θ], Subscript[(Subscript[σ, s]), BB],
TraditionalForm@Subscript[Π, BB][θ]}, LegendFunction -> Framed], {0.86, 0.5}]]


Use LegendFunction -> "Frame" to get