How to indicate in Chinese text that a quote has been translated from English?
Once an English sentence is translated into Chinese, you can treat it as Chinese.
(上引号 - upper quotation mark) = 「
(下引号 - lower quotation mark) = 」
Tom said &quot;I have a house&quot; = 汤姆说：「我有一套房子」。
It is very common for people to use English quotation mark in Chinese text, there is nothing wrong with 汤姆说：“我有一套房子”.

In a Chinese text, if I used a quote that was in English, but was translated into Chinese, how would I indicate this?

I would write:
汤姆说：「我有一套房子 (I have a house) 」。
汤姆说：&quot;我有一套房子 (I have a house)&quot;.
If you don't want to use English in the sentence at all, you can write:
汤姆说：「我有一套房子 (英文) 」。
汤姆说：&quot;我有一套房子 (英文)&quot;.