In brief, applicants submit an Expression of Interest form to Immigration Canada summarizing their skills and credentials. Following submission, applicants are entered into the Express Entry Pool of individuals with similar career backgrounds. Whether you rank higher or lower in the Pool will completely depend on how you present your initial application.
The highest ranking candidates will periodically be invited to apply for Canadian Permanent Residence. After you receive an Invitation to Apply, we'll only have 90 days to submit a complete Application for Permanent Residence, which would include documents concerning your finances, medical exams, police records, job references, and many others.