Can't seem to find the right settings

I'm trying to follow this tutorial https://youtu.be /98gKfdJRzro but then at 32:00, when he checks the box to activate Ambient occlusion, my settings menu looks totally different than his and I do not have any possibility to check somewhere there to activate AO. Am I doing something wrong ?

I'm trying to follow this tutorial https://youtu.be /98gKfdJRzro but then at 32:00, when he checks the box to activate Ambient occlusion, my settings menu looks totally different than his and I do not have any possibility to check somewhere there to activate AO. Am I doing something wrong ?