You don't need to apply to the exemption. You would do a regular application, and ignore the biometrics letter (in case u receive it). You would need to keep checking as well if they change these rules and restart to take biometrics for your type of application (and in this case you would have to go after the biometrics). You can check the specific biometrics rules for your type of application over here:
https://www.canada.ca/en/immigratio.../services/coronavirus-covid19/biometrics.html
You can check if you gave biometrics and it is still valid through this link :
https://onlineservices-servicesenligne.cic.gc.ca/extapp/bioStatusQuery.
If yes, I believe you could pick "yes". However, if is still unclear, I would suggest to choose "no" (in order to avoid future complications).