I think that you only have payslips if you worked for someone, so I don't know what you mean when you ask if you should add them. Unfortunately, anything that lasted 3 months, does not fit any NOC, and only gave you a certificate, would not count towards CRS points.
For it to count for Education, it should have lasted more than a year and even so it would need to "count" as one for any of the ECA agencies.
For it to count for Work Experience, it should have been paid, fallen within one NOC, and been for at least 1-year (unless you already had a job that lasted for a continuous year or more)