Learn English – How should I translate “take as input”

When you "raise a point", you are bringing up an issue to be discussed. After someone has raised a point, you can refer to it as "the point [that has been] raised."

One possible sense of take is consider, as in "take, for example, the lowly worm." (You are not being asked to physically acquire a worm, but to think about some aspect of it.)

Thus, when you want others to examine the issue that someone brought up, you can ask them to "take the point raised".

The "sign" in this case is a metaphor. It's based on the convention that individual shop-owners and craftsmen* had of putting a sign up in front of their business to say what they were: a blacksmith, perhaps, or a tailor, or whatever else. The sign might be written, or, especially in even earlier days, might simply be a picture representing the shop's purpose.

So the "sign" the jay has is all those human-like characteristics being described, as though the jay were in business as a professional human. Twain is saying, well, if he's not a human, he should stop acting so human — take that sign "inside" the metaphorical shop where no one will get misled by seeing it!

_{*Individuals in business by themselves were more common at the time of Mark Twain.}