You can use transitions on any titles, just like you can on video clips. Transitions can be dropped at the start or end of a single title or across two adjoining ones.
You can also use keyframes in the Title Designer. Set the Opacity at 0 at the start of the clip and then at 100 at whatever point you want the fade to finish.
Another option is to select Fade from In Animation on the Animation tab. Note you must set Title Designer to Advanced mode to see the Animation (and Motion) tab(s).