我报名参加了用英文怎么说

"I have enrolled in" 或 "I have signed up for" 是表示 "我报名参加了" 的常用说法。

"Enroll" 和 "sign up" 都有 "报名参加" 的意思。
"Enroll" 来自拉丁语 "enrollare"，意思是 "提名，登记"。
"Sign up" 来自英语 "sign"，意思是 "签名"，和 "up" 意思是 "向上"，合起来就是 "签名向上"，也就是 "报名"。

例句:

I have enrolled in a cooking class. (我报名参加了一个烹饪课。)
I have signed up for a marathon. (我报名参加了马拉松。)