If your family composition has changed you have to inform IRCC and they will send you the forms that you have to fill in and send back.
After you marry, you can send a webform and inform IRCC. IRCC will send you some forms and ask for the following documents:
1. An IMM8 Application
2. Schedule A form for spouse
3. Additional Family Information form for primary applicant and spouse.
4. Fee receipt for spouse - Processing fee ($550) and right of permanent residence fee ($490).
5. Birth Certificate of spouse, translation, and affidavit of translation.
6. Copy of Spouse's Passport
7. Copy of marriage certificate and marriage registration
8. Wedding Card and Photographs
9. Police clearance certificate for the primary applicant and spouse
10. Spouse's upfront medical
11. Letter of Explanation (If required)
Your application will be reopened and after your spouses documents are processed, both, you and your spouse will be issued new COPRs (if your spouse is accompanying). This takes 2-4 months. In this process, your eligibility is NOT re-evaluated. See
https://bit.ly/3gGuOC8