Use this calculator to find the cage size requirements:
link
Mice are fairly easy to take care of. If they're new mice (I'm assuming they are), it'll take awhile for them to get used to the new surroundings. If they're not used to your smell, they'll likely run away from you. Just stick your hand near them, but don't chase them. They'll come towards you. You should play with them at least an hour everyday.
A wheel, water bottle, and some type of bedding (don't use newspaper) are necessary. You can add chewing things and toys (such as ladders, swings, tunnels, etc.) so your mice won't be too bored. You might also want to get a pet dish so the food can be kept relatively fresh (make sure its heavy as mice tends to tip it over). You should change your water bottle every three days or at least once a week. Cleaning the cage also requires that you clean at least once a week (or every three days if it gets dirty really quickly). You have to keep track of their teeth so it doesn't overgrow.
