The exact meaning of endorse can depend upon its context. For example:
"I endorse her candidacy." — support for a candidate
"I endorse the committee's recommendations." — support an idea
"She is paid a million dollars a year to endorse the company's products." — publicly support in return for payment
"She endorsed and deposited the check." — approved placing funds into a bank account by writing something like "for deposit" and signing the back of a check
Where, to be allowed with love, would be the endorsement of the world, that it was not the barren confusion distant dry fears hinted and whispered, but was necessary, justified, the justification proved by joy.
Chapter 8 (56% in)
There are no more uses of "endorse" in The Adventures of Augie March.