Answer: How? I shall explain...
Step-by-step explanation:
So Biotechnology is the mix of natural sciences and engineering sciences in order to achieve applying organisms, cells and organic matter for products and services.
Think about if someones DNA has malfunctioned and the scientists need to change it. They use bio-engineered cells to go in the nucleolus of the cell and edit the DNA. (To the best of my tiny knowledge)
Scientists can't perform molecular sized operations for cells and organisms, so they use bio-engineered cells to do it. (Tell me if I'm wrong)
They can also create situations in contained environments to experiment with modified cells to see the results.