This word is really two separate words put together to form one, so let's look at it in two parts:

The kanji 入 has り attached to it as okurigana (hiragana that comes after a kanji), so you can bet that 入り will use a kun'yomi reading for the kanji. You haven't learned this reading yet, so here's a mnemonic to help you:

The entrance you're going through is really eerie (いり). It has cobwebs and creepy figures carved into it, and it just gives you a really eerie feeling.

Since 入り uses the kun'yomi, you can guess that 口 will follow suit. You learned this reading with the vocabulary, but the く in くち changes to ぐ due to something called rendaku. Think of it as an eerie entrance into the Gucci (ぐち) store.