You want to add French $($Canada$)$ to your list of Editing Languages so you can make sure that your spelling and grammar are correct in any documents that contain French. You would do this by:

a$.$

Going to File $>$ Options $>$ Language $>$ Choose Editing Languages $>$ Add additional editing languages and select French $($Canada$)$ from the drop$-$down list. Click Add.

b$.$

Going to File $>$ Options $>$ Proofing $>$ When correcting spelling spelling and grammar in Word $>$ Add $>$ French $($Canada$).$

c$.$

Going to File $>$ Options $>$ Language $>$ Choose Display and Help Languages $>$ Add additional editing languages and select French $($Canada$)$ from the drop$-$down list. Click Add.

d$.$

Going to File $>$ Options $>$ Proofing $>$ When correcting spelling in Microsoft Office Programs $>$ French Modes $>$ verb forms only.