Even for the experienced divers the use of scuba dry suits means learning to dive again. There are many places where you can take a course to understand well what is a dry suit and how to use it. Let's understand the concept of this type of suit: they are air receptacles. This translates into some trouble when you try to control your buoyancy. The first consequence you can face is that being airspaces, scuba dry suits get compressed as pressure gets higher. The compression will make folds, squeeze and pinch. To prevent that, you simply need to let some air in the suit through the chest valve as you descend.
As you dive you can easily loose track of basic security precautions. Imagine for example, a situation in which you get distracted because something gets your attention in the bottom and you go for it head down. All the air in the dry suit will go them to your feet (your highest point)and expand as the pressure there is smaller. So, you are suddenly pulled up and struggling to regain control of your buoyancy. This quick ascend can be very dangerous as you can get the decompression sickness (DCS). Don't panic! What you need to do is to bring air to the upper part of your body so you can release the excess of it through the valve in your arm. In order to do so, the trick is to roll yourself into a ball and them turn till your head is up.
Scuba dry suits are great tools to make you have great diving experience, like sub aquatic photography or exploring shipwrecks. but make sure that you are well trained before getting inside one.