have you read the application guide yet? this information is in there:
http://www.cic.gc.ca/english/information/applications/guides/5525ETOC.asp
There are 2 applications: the sponsor application and the application for PR. The sponsor fills out the forms for the sponsor, and the person seeking PR fills out the applicant forms. Both sets of forms are sent TOGETHER in the same package along with all the required documentation listed on the checklists. If the sponsor and the applicant are in different countries, then the applicant needs to fill out/sign/validate all her forms and then send them to the sponsor so the sponsor can submit all forms together. The forms that require signature can not be faxed or scanned, the originally signed form must be submitted.
The guide linked above has all the information you need. the checklist shows you which forms are to be filled out by the sponsor and which forms need to be filled out by the applicant. both people can certainly help each other fill out the form, but each person needs to make sure the information being presented is truthful and sign their own forms.