My goal at the moment is trying to enter the blue building. But the only step I don't really get is:

-Have at least 1 pet with an overall rating of 100 or more.

What are pet ratings, how do you get there and how do you improve them? I'm pretty new, so I'm sorry if this is an obvious question.

one's just phrased oddly. It just means you need your pet's stats, not including level or intelligence, to add up to at least 100. So if you train them all to 25 each, you should be able to get in.

Thanks! :)