You can find more walkthroughs as well as material guides and recuitment tips here. This guide is to get Rosemon Burst Mode but the underlying principles apply for all DNA Digimon.
Do not stand there in awe, you got a world to save. Because of this, with some time and planning you can get 2 DNA Digimon. In Digimon World: Next Order, your two Digimon will combine to form a more powerful Digimon while the other will De-Digivolve into a lower form. DNA Digivolution was introduced in Digimon Adventure 02, where two Digimon would combine their powers to merge into a singular entity whose sum was greater than its parts.