I am installing a new system on my iMac. When I get to the terms and conditions, the agree arrow is grey. How do I continue to set up the Mac?

I'm not sure of which you are referring, but often time you have to scroll to the bottom of the text for the agree button to become enabled.

Scroll down to the bottom of the Terms & Conditions. Does the agree button then light up as selectable?

Follow previous advise - First

Have seen some suggestions to Log Out of iCloud completely and then try again

I have the same issue

I have the same issue

I assume that you likely read all the previous responses to your "same issue." What was the result of following those suggestions?