我在铃响前刚好有时间吃完，然后就去上第一节课了。

I had just enough time to finish eating before the bell rang and I was off to my first class.

《柯林斯英汉双解大词典》

来上第一节课就行了。

Just turn up for the first class.

youdao

现在我又急匆匆地来上第一节课。

Now I rush to make first period class.

youdao

I announced on the first day of class that I don't, myself, believe in the existence of a soul.

第一节课上,我就声明,本人并不相信灵魂的存在

耶鲁公开课 - 死亡课程节选

Today. So this is the first class, the first moment of shopping that you guys are going to!

所以这是第一节课,这是你们上的第一节试听课

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

Now that definition, if you're worried about what I've written down here and you want to see it in words, on the handout I've already put on the web that has the summary of the first class, I included this definition in words as well.

对于这个定义,如果你还有些疑问,而且你想看用文字表述的,在讲义中有,我已经上传到网上了,里面有第一节课的总结,也这个定义的文字形式

耶鲁公开课 - 博弈论课程节选