Sale of main home and purchase of new home and CGT due

I sold my home I had owned for 30 years and downsized to a smaller home.   Obviously the price of property has increased dramatically over 30 years and so I have a huge capital gains ($590K).  All of that money was used to purchase my smaller home.  I can't see where I can record that on my return, and when I researched it, it said that the purchase of your new home is irrelevant to the return and you can only claim for mortgage/interest etc. So I'm left showing a huge CGT, and it shows I owe about $82K in taxes, which I don't have!!  I am over 65 years old.

What should I do?