The same mechanism a virus uses to use a molecular key to open a door into a cell in hopes to hijack cell processes to grow copies of a cell.

In DNA there are no such mitochondrial factories so maybe only a segment of only a few AGT or C sequences replace original code, do not get reproduced but stored and copied to the warehouse to one day get replaced by another segment 200 years later.

In short a bit of DNA hitch hikes on a virus.

Maybe it only replaces DNA that is already in the junk warehouse section of our genome. Otherwise it will be corrected by RNA matching code correction.

Answers to this question is beyond me but what experts are probably looking for.