Logic Pro X Studio Horns Vibrato


Hi everyone
Really struggling with this. Looked on YouTube etc, etc and can't seem to make it work.
Does anyone know how to control the depth and speed of the vibrato?

I'm trying to get vibrato to come in on the end of longer notes to make things feel a little more "human" but I'm not getting any vibrato at all.
I thought that it was assigned to the Mod Wheel but that isn't make any difference.
Any thoughts?
Thanks in advance for any help.