When you set a keyboard combination with more than 1 key you have to hold them all down at the same time. So for this one you just need to press and hold on CTRL and then press F10. Of course you might need to hold down the Fn key to get F10 depending on your keyboard setup.
And if you still have trouble you can use the windows on-screen keyboard. Just click on the arrows I’m showing from left to right.
