Use the Default Text and the alpha (i.e. transparency) issues are taken care of for you.
To make the text longer, place your cursor on the right or left side of it and drag it out to the desired length.
Here’s a hint to make your text look a bit cleaner (especially around the edges). Double the size when you create it. That is, change 720 x 480 to 1440 x 960. The boxes for this are in the top left of the titler event FX window.