First, go to
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/account.html
Scroll down and click on
Continue with GCKey
Sign in or Sign up and then Sign in with the Principal Applicants credentials (one who is being sponsored)
Click on
Add (link) your application to your account
Select Category: Permanent Residence
Sub Category: Family Class (Spouses)
Select: Family Name, Given Name and Date of Birth
Family Name: Fill in the Principal Applicant's last name
Given Name: PA's first name
DOB: PA's
Select: Passport
Fill in all the details
Select the intended/current Province and City of the PA and Marital Status
Enter the number of family members as 2 if the PA has no dependent; otherwise, add 1 for each dependant on the application.
Good luck and let me know how it went.
Please note the instruction is for Inland Applicants only. For Outlanders, there will be a bit of a tweak to it.