To Register
する verb
登録 is registration. Make that into a verb and you have to register.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
無料で登録することができますよ。
You can register for free.
新しいアカウントを登録するにはメールアドレスが必要です。
You need an email address to register a new account.
登録するだけで特典がもらえるんだって！
Apparently, you get perks just by registering!
臓器提供者として登録をしたきっかけは何ですか。
What motivated you to register yourself as an organ donor?