If you click the question mark next to Purpose of Travel, it will tell you to upload things like flying ticket. However, most people won't book tickets until they have the work permit. So what we do here in China is to upload a LOE explaining why you are applying, what you will be doing in Canada and what you plan to do when the work permit expires.
For client information, it's quite similar to study permit. Upload materials relating to
- the relationship of the principal applicant and the open work permit applicant, such as marriage certificate, joint bank account, joint property, a love story letter, family pictures, etc. (If you guys are a newly married couple or common-law partners, it's better to provide more materials to prove your relationship)
- the financial status of the spouse (similar to study permit but fewer funds are required);
- the education and employment history of the spouse (to show the spouse's ability to work in Canada); and
- others materials such as a police certificate...