Do you mean the section at the top of pages 2-7 with a black border/frame around it? If so then that should be the sponsors name
Just for reference in case you don't know:
Sponsor = applicant
Principal applicant = the person being sponsored (the spouse, common law partner etc...)
By the way, this section would be filled in automatically if done by computer, so im assuming your filling it in by hand? If so I'd recommend you to fill in the forms by computer,This way there is less chance of making a mistake, considering you can easily validate and check for any missing spaces before you finalize your document.