YOU SAID:

then you line is "how did you know that?"

INTO JAPANESE

それから、あなたはどのようにそれを知っていましたか？

BACK INTO ENGLISH

And how did you know it?

INTO JAPANESE

あなたはどうやってそれを知ったのですか？

BACK INTO ENGLISH

How did you get to know it?

INTO JAPANESE

どうやってそれを知ることができましたか？

BACK INTO ENGLISH

How did you find out about it?

INTO JAPANESE

あなたはどうやってそれについて知りましたか？

BACK INTO ENGLISH

How did you hear about it?

INTO JAPANESE

それについてどうやって聞いたのですか？

BACK INTO ENGLISH

How did you hear about that?

INTO JAPANESE

それについてどうやって聞いたのですか？

BACK INTO ENGLISH

How did you hear about that?