App-specific passwords are a security requirement put in place by Apple. You MUST complete this process before you can connect iCal to Maple.
Visit https://appleid.apple.com/ and sign into your Apple account with your ID and password.
You'll want to scroll down to "App-specific Passwords" and generate one with the name "Maple"
Once you've been successful you should see a screen pop up with your App-Specific password for Maple. BE SURE TO COPY IT ON YOUR PHONE you can just use the copy function or write it down (whatever you prefer).
Open “Calendar Settings” and navigate to “External Calendars”. Then select “Apple”.
Follow the prompts to connect your calendar. You'll be asked to input your Apple ID and the App-Specific Password you generated in Step 1.
Once connected - You'll have the option to select which calendars you would like to link to Maple. These calendars can be adjusted in Account Settings within Maple.
You'll also be given the opportunity to choose which (if any) you'd like to share visibility to those calendars with.