Check blood pressure by fitting the cuff snug on the arm, placing the gauge where it can be seen, but is still in line with the brachial artery, and putting the stethoscope over the brachial artery, as well. Pump up the blood pressure cuff and listen for the first and last beats of the heart with instructions from a nurse in this free video on blood pressure.
This is how to do a blood pressure correctly. You put the cuff on the arm. You have the arm resting either on you or the table. You put the monitor, the gage, where you can see it. It also has to be in a line with the brachial artery. You put the cuff and make sure that it's nice and tight and snug. Put the stethoscope in your ears. You put the bell of the stethoscope on the brachial artery, and you pump up the gage until over and above what you think it might be, but always go a little bit above. Wait to see if you hear anything, like a loud sound. The first loud sound that you hear is the top number. You wait. You go down slowly with the gage in your hand, and the last number that you hear that's loud is the bottom number of the blood pressure. Then you let this out very slowly. If you have to start over again, what you would do is that you would pump it back up again, and start all over. But you let it completely out first, and then start over again if you're not sure of what you heard. You then, after it's been completely let out, you take the stethoscope down, supporting the arm. And you take the cuff, and you pull it off, and put back what you had pulled up, there. And, put the arm down by the patient's side.