A 7 speed shifter won’t work with a cassette other than 7 speed. If working on it doesn’t appeal to you, I suggest using a bike shop to get it set up.
I will ask my local bikeshop if they can help me.
Many thanks for your help paul!
I would encourage you to give it go yourself.
Describing the steps is actually harder than performing the task.
You will learn a lot about bikes and hubs etc and that will make you a more educated cyclist.
If you currently are not performing your own tune ups on your bike, this exercise will help you understand how to perform many basic processes that make the bike run smoother.