When you select the kind of title you want, a window will open where you can work with the text, and you will see a preview in the preview monitor on the right.
Except for the last option (“Add credits at the end of the movie”), all the titles work the same way. You will see two boxes: text entered in the top box will be bigger, text in the lower box will be smaller.
Don’t worry if you don’t like the font, or if you want to change the way the title moves – you’ll be able to change this later. You can see a preview of what it will look like by pressing Play in the preview window.
When you’re ready to add your text to your timeline, simply click “Done, add title to movie.” However, there is a lot you can do with your titles, and you should explore!