How do you play multi player in Mario party 8?

Simple. You must have more than one Wii Remote connected. To connect multiple Wii Remotes, press the Home button on a Wii Remote and press Wii Remote Settings. Then click Connect Wii Remotes. Press 1 and 2 for a temporary sync or the red sync button under the battery cover and the red sync button under the Wii SD slot to permenantly sync. Then, just select 2 or more players!

Also remember there is 1-4 and single player options after start screen so some games are only single player.:)