The notice provides all the basic info.
If you qualify, then you don't need to do anything to participate. If you want to pt out, the deadline is Oct 28, 2021.
For more information the notice mentions:
The lawyers for the class are: Gowling WLG (Canada) LLP (Toronto); Michel Drapeau Law Office (Ottawa); Murphy Battista LLP (Kelowna and Vancouver); Koskie Minsky LLP (Toronto); McInnes Cooper (Halifax). To learn more about the class action, including whether you might be a class member or how to opt out, please visitwww.vetspensionerror.ca. Any questions about the class action can be sent firstname.lastname@example.org