mrigi = deer
mudra = seal
Step by Step
Ball your right hand into a fist. Press your index and middle fingers into the mound (or base) of your thumb, so they're held firmly in their curled position. (This mudra is traditionally made with the right hand, but there's no compelling reason why left-handers can't use their dominant hand if they like).
Stretch out the ring and pinky fingers. Keep your pinky relatively straight, but curl your ring finger slightly, then press its pad to the pinky's nail. Align the fingertips as best you can; the idea is to "blend" the two fingertips into one.
Now bring your hand to your nose. Be sure not to turn your head toward your hand, keep your chin aligned over your sternum. Also be sure to keep your right shoulder level with your left shoulder. Tuck your right elbow in close to the side of your torso without hardening your armpit.
For all digital practices, the ring finger/pinky pair will close the left nostril, the thumb the right (unless you're using your left hand). Curl these fingers so that you press the nostrils with their more sensitive tips, not their pads. When you close a nostril, apply just enough pressure to block the opening, not so much that you interfere with the flow of breath through the open nostril.
Try this simple practice. Close your right nostril and inhale slowly through your left. Then close the left and open and exhale through the right. Finally inhale through the right, close it, and open and exhale through the left. Repeat 2 or 3 times, then release the mudra and breathe normally for a minute.