enable context menu for murder gamemode

i have tried adding but it doesnt work ,
function GM:ContextMenuOpen()
return true

im not a master at lua coding though , any help would be appreciated.

hook.Add("ContextMenuOpen", "BlockContext", function() return false end)

thank you sir,
im sorry for sounding stupid , but where do i put this code

Clientside, so lua/autorun/client will work.

it doesnt work , i put the codes into a new lua file i created inside lua\autorun\client and i still cant access the context menu.