Go back to the decks screen.
Click the deck settings: the gear at the right edge of the line that starts with the deck name.
Select 'Options' from the context menu.
You should be on the 'New Cards' tab in the 'Options' Window. If for some reason you are on another tab, select 'New Cards'.
The second line of the 'New Cards' tab is 'Order'.
The order setting is probably 'Show new cards in random order'.
The order setting is a drop-down; click it, and select 'Show new cards in order added'.
You may want to consider creating a new 'Options group' (at the top of the Options window) to have separate options for the deck.
If you studied any cards, you may need to reset progress in the deck.