The easiest way to break the movie up is to use Save As to create 3 or 4 copies of your project -- then just cut each project's timeline so that it is only a segment of your whole movie.
A DVD can hold about 70-80 minutes of video at full quality.
I agree with Steve G. on the best (also the easiest) way to break up a Timeline, into smaller parts.
If you look at his last sentence, regarding the Duration of the Timeline, the first question that we need answered is "How long is the Duration of your Timeline?" That will be the first indicator, whether you need to break apart your Timeline.
Depending on the answer to that question, regarding your Duration, another option might be to use a DVD-9 (Double Layer) blank disc, rather than a DVD-5 (Single Layer). The DVD-9 would allow for about twice the Duration.
Good luck, and please let us know just a bit more about your Project.