Here's a link to Shimano's exploded view PDF file for the Deore FC-M510 series.

LINK

Click on the plus sign (magnify) button on the PDF toolbar and enlarge the image to 300% or more, until you can really see the details in the illustration.

There should be a tab on the inner diameter of the chainring, between two of the stack bolt holes.

That's your placement indicator. It should be in line with (under) the right crank.

In the illustration, the '4' in a circle is almost pointing at the inner chainring's tab Shimano calls it a 'salient'.

Also in the illustration, the (lower) '6' in a circle is pointing right at the chain drop prevention pin, which is on the large chainring.
If yours doesn't have a chain drop prevention pin, but has chain lifter rivets on the face of the ring, below the teeth, the flush side of the rivets should be on the crank side, and the protruding side of the rivets should be should be facing the middle chainring.