Start out by going to the Effects Tab in your Browser. Go to Video Generators > Text > Scrolling Text. Load the Scrolling Text generator into the Viewer window. You can also reach this option from the Generators menu at the bottom of the Viewer window.
Once the Scrolling Text Generator is loaded into the Viewer, bring it into your Sequence, and then load it back into the Viewer. This will protect you from accidentally loading something else into the Viewer, which would cause you to lose all your work if you hadn't brought it into the Sequence. More important this will allow you to park your playhead over the Scrolling Text Generator in the Timeline, and see it in the Canvas, thus allowing you to see the changes as you make them in the Controls tab.
Click on the Controls Tab. Now you are given a Text Box where you can type your credits into. Be sure to break up each line of text by hitting the Return key.
You can also change the parameters of your scrolling text credits by changing the Font, Size, Style, Alignment, and Color of your text. The Leading percentage can usually be left
at zero, which creates a blank area at the beginning of the text. The scrolling credits duration can also be adjusted in the Video Tab in the upper left corner. If you want them to move a little slower up the screen, increase the duration, or if you want them to go by quickly, decrease the duration. It's something you'll have to play with to get the look you want.
To have the scrolling credits over top of video or a still frame, place the text you created on top of the video in the Timeline. In the video example I used, I had to bring down the opacity of my still image in order for the white text to show up a little better. If you need to produce another Scrolling Text that will have the same attributes, you may want to Match Frame the text. This will make it easier to produce another with the same attributes.
So as you can see, simple scrolling credits are easy to create in Final Cut Pro, and they will add to the professional look of your video. For more information on creating text, check out this article to help make your text "pop".