Beforehand
In Advance, Previously, Ahead Of Time
adverb
The kanji and the word are almost exactly the same. That means they share meanings as well.
Note that 予め is mostly used in formal contexts like meetings, announcements or notices, and business emails.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
At the Last Supper, the apostles asked beforehand: "Can we order à la carte, Jesus (あらかじ)?" Jesus said no, but He also knew ahead of time that Judas would betray Him by ordering some expensive à la carte dishes. And also by doing that other thing.
予め決める
to decide beforehand
予め作る
to make ahead of time
予め用意する
to prepare ahead of time
こうなることは分かっていたので、予め用意しておきました。
I knew it would happen, so I prepared ahead of time.
予めフライト前日にオンラインでチェックインしておきました。
I checked in online on the day before the flight.
予め予習しておいた甲斐がありました。
Preparing the lesson in advance was worthwhile.