Start by verifying zero with the jaws closed. 

Turn the ratcheting knob on the end till it clicks.

If it isn't zero, adjust

Carefully open and close the jaws around the specimen using the ratcheting knob till it clicks.

Read it!

First, identify that it's between 3 and 4 (0.3)

Next, see that it's just past the quarter mark (0.325)

Also see that the dial reads between 4 and 5, so add 0.004 to the 0.325 = (0.329)

To get the ten-thousandths place, read the vernier.

Look for the line that best aligns with a mark on the dial - in this case 4.

So add 0.0004 for a final reading of 0.3294