Well, you are going to need an NLE which is a video editor. There isn't a "best one" as it is completely up to your personal preference. For instance, I use Adobe CS3, whilst others use Vegas. If you're on a Mac, you can use Final Cut Express or Final Cut Pro (HD). Free ones (which aren'tr nearly as good but could get you started) are iMovie and WIndows Movie Maker
Those are just some examples. You can use the NLE to cut video, add transitions, titles, etc and then export (render) to any of the FXHome Labs programs.
In addition to an NLE, for sound ediintg, you may find that a program, like Soundbooth, Acid or Audacity (free) will help tremendously. You record and edit sound in the program and then export it as an MP3 or whatever file you choose and then open it in your NLE. Add it to the clips in your timeline and the ones from the FXHome program, render, and you have a nice movie. Though an NLE can handle the basics for sound, often times you'll find a seperate program opens a new world of possibilities. Even a free one like Audacity which is suprisingly fairly powerful.
Hope that helps!