If you open the image in PS all you need to do is press the "T" key (it's the shortcut for the type tool). Type your text and then on the top you will see a circle with a slash thru it or a check mark. Click the check if you like it. You can adjust the type size by highlighting what you wrote and then using the box with the #pt next to it. Bigger number, larger test size.
For the opacity Beerguy mentioned go to the "window" drop down menu up top and be sure "layers" is checked. You will see the text layer and in the layer box up top you'll see opacity. Decreasing the value will make it sort of see thru.
I learned by playing around. Took forever, a class is a good idea. Even a book. There are also tons of online tutorials on it. Before you know it you'll be swapping peoples heads and cloning out annoying dust spots like a pro!