@ehdog

It's too tight if it's making your arm numb before it even starts inflating or if it doesn't wrap around your arm at all.

It's also high enough. There's nothing you've described that suggests you're doing it wrong.

@ehdog

No. First off you should be able to slip 2 fingers under the cuff in the front. In your case maybe not 2 if they are fat. It should not be tight.
#2 The front of the cuff should be about an inch from the crease in your elbow. You have it too low.
#3. The air tube coming from the cuff should point to the middle finger of your hand. If there is a mark then this should point to the middle finger. There is a doohickey in the cuff that cuts off the blood flow by squeezing on the artery. As the pessure is relaxed the point at which blood starts to flow is your systolic number. When the artery is fully open that gives you your diastolic number.

I do not know if cuffs are interchangeable among/between brands.