When using quotations, it is always recommended that when possible the original source of a quotation is located and used, however that is not always possible.
Very famous quotes that are easily recognised and very well known do not need to be referenced e.g. "To be or not to be, that is the question".
This example is of a quote purported to be from Plato, but it is not possible to find the original as not enough information is provided.

So within your text, credit Plato as the original author of the quote, but reference the picture above in your reference list, like so:
In-text citation
Plato is credited with the quote that "the greatest wealth is to live content with little" (as cited in BrainyQuote, n.d.)
Reference List
BrainyQuote. (n.d.). Plato quotes. https://www.brainyquote.com/quotes/plato_110191

In-text citation
The famous I have a dream speech is an example of... (King, 1963).
Reference List
King, M. L. (1963). “I have a dream…”. U.S. National Archives and Records Administration. https://www.archives.gov/files/press/exhibits/dream-speech.pdf
If you omit material within a sentence when quoting, you need to use 3 spaced ellipsis points (3 dots), like so:
In-text citation
Rich (2009) agrees that the "reason we all enjoy ice cream is the ... taste" (p. 157).
When omitting material between two sentences, use 4 points. The first point indicates the full stop at the end of the sentence.
The 3 spaced ellipsis points follow, like so:
In-text citation
Rich (2009) agrees that the "reason we all enjoy ice cream is the fabulous creamy rich taste. ... a world without icecream is a sadder place" (p. 157).
There are certain words in the English language that are spelt slightly different depending on where you are e.g. organization (American spelling) vs organisation (British spelling). There may also be spelling mistakes within certain sources as well.
APA rules state that you cite what you sight. That means you keep the spelling exactly as it appears within the quotation.
If you wish to indicate a change of a word, capital letter or a spelling mistake when referencing, use the following guidelines:
In-text citation
As Sally Jones (2006) remarked in her book Bike, "we would of (sic) won if we didn't get a puncture, but [the roads] were just too bad [emphasis added] to ride on" (p. 56).