Put one reference in reach
Share the same rule page with all four players. Record any house changes before starting. Ask everyone whether they have played this exact version rather than whether they already know the game.
Make room to learn
Keep an area clear for played cards and a separate place for notes. Choose a person to explain the selected rules, while allowing anyone to stop and ask for a reference. A confident explanation can still be mistaken.
Practise without a result
Walk through one open-hand example. Describe each choice before moving a card. If an explanation depends on an unconfirmed house rule, settle that question first; do not carry it into a scored hand.
Keep the first session small
Finish by recording one thing everyone understood and one question to revisit. More hands are not a substitute for understanding the point of the last one.