Using Spouse's IELTS score

My friend wants to use her wife’s IELTS score in his application. What’s the procedure for this?

Please clarify what you mean by ‘use’ wife’s IELTS.
If you mean your friend wants his wife to be primary applicant. Either of them can be primary applicant. They can decide it based on whichever option fetches a higher CRS score.

Thanks. My friend has a master’s degree but his spouse has only a bachelor’s. So can he be the primary applicant and use his spouse’s IELTS score for the application or does she have to be the primary applicant?

Since your friend has a master’s degree, he’d most likely have to be primary to get a higher CRS score.
You can calculate estimated scores by choosing either as primary, and comparing.

Primary applicant has to provide English test scores (IELTS or others). spouse can also provide her IELTS to get a higher score. i.e. its mandatory for primary, and optional for spouse.

Thanks, How about WES evaluation, do they both need to get it done or only the primary applicant?

They would get additional points if both get the evaluation done.