The First Step, First Step
noun
第一 means "the first," and 段 is a step. So, this is the first step.
だいいちだん
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.
では、第一段は森さんが読んでください。
Now, please read the first section, Mr. Mori.
やっぱりどのテレビ番組でも、第一段目の席には、人気アイドル、人気芸人、人気俳優が座るんだね。
In any TV program, it seems that popular idols, popular comedians, and popular actors always sit in the front row, after all.
第一段階として、まずは基本の復習をしなくちゃいけないかもしれない。
I may need to review the basics for the first step.