How to add rotation to a CFrame?

I have an model, and I need to get a random rotation,

Local model = --whatever model
local cFrame = CFrame.new(0,0,0)--the CFrame is obtained through other calculations

local randonRotation = math.rad(math.random(1, 360))

--This is an imaginary scenario
cFrame:AddRotation(randonRotation , 0, 0)

model :SetPrimaryPartCFrame (cFrame)

so the model is going to have a random rotation in X axis, but I don't know how to add the rotation.

Any help would be appreciated.