1) Go here to download the client: https://clientdownload.catonetworks.com/
2) Follow the directions here to install the client and allow it to do what it needs to on your Mac: https://support.catonetworks.com/hc/en-us/articles/7955190904989-Getting-Started-with-the-macOS-Client
3) Once it is installed, you should be able to log in with your WOL provided account.