Because there's some okurigana (hiragana attached to the kanji) attached, you can bet that 入り will be a kun'yomi reading. This reading comes from the word 入れる. If you know that word already, this one will be easy. If not, then you'll have to think that the entrance you're going in is eerie (いり). Then, because this word is really two separate words put together to form one word, you can guess that 口 also uses the kun'yomi reading, though the く in くち changes to ぐ due to something called rendaku. Just remember that it's ぐち and not くち here.
I will wait for you at the entrance.
There are three entrances.
Johnny Depp is at the entrance.