How do get a job record onto my highschool transcript?

I've been planning to work on one of parent's friend's firm/company (note. we are not related by any mean). But I as I've been planning this thing out, I don't know how to show the school evidence that I've work there. Do I get the owner to sign some kind of a document/contract? Or do I just tell the school?How do get a job record onto my highschool transcript?
Transcripts are for grades only. If you are applying to a school, the application should have a place for work history where you could list this job. If not, send in a resume that details your work history. Again, transcripts are only for grading records.