Grasshopper-Rhino Link

Hi Folks

I'm new to grasshopper and trying to get my head around the basics and hopefully learn it quick. I've a question that might be very basic to you guys but I would be grateful if you can help me. When I start Grasshopper the changes that i make to the parameters won't appera instantly in Rhino. While i look at videos on here and in all cases i see that when you change a parameter in Grasshopper the effect appears immediately in Rhino. Do I need to change a setting?

Regards,