Click on the button at the top of the date column.

Or use the menu. View|Sort By…

After sort by what do I click on there is a long list

Well, Date, naturally since you want to sort by age. And then repeat the process but select Descending for newest first.

Or just click the Date button again. If you click a button you select that column to sort on. If you click it again and it's one that sorts, then the sorting order is reversed. Most of the columns sort, the notable exception being the "thread" button, which instead toggles threading on and off. If you want strict chronological order, you need to switch off threading.

My "Date" button has an arrow, like △ or ▽. On mine, "newest first" corresponds with △.