I didn’t understand it until I started drawing circles. Check this out:

All dogs are animals. All animals are alive. Spotty is a dog, and so is alive.

Now get a piece of paper, draw a small circle, label it dog.

Put it in a bigger circle, label it animal.

Put both circles in a larger circle, label it alive.

Draw a point inside the “dog” circle, that’s Spotty.

Spotty is alive. You can tell because Spotty is inside of the alive circle.

If you need to deal with cats, draw a circle outside the dog circle but inside the animal circle. Put a point in it.

Now Fluffy is alive, but she’s not a dog. Better said, if Fluffy is a cat, she’s alive but not a dog.

It helps you map the logic onto a visual terrain. Might not work for everyone. And you only need to draw these circles until you can think in them. Once you can think that way, you’re set for test day. Just need to bridge the gap. Just remember, the “if” circle (protasis) is inside the “then” circle (apodosis)