If you'd like to schedule directly through your calendar, you'll just need to remember to include firstname.lastname@example.org as a guest/invitee, and you'll need to include the link to the Interview Kit within the description of the invitation.
There are a couple of places where you can grab the link to the Interview Kit without going through the process to schedule the interview. When you are on the candidate profile page, if you hover your cursor just to the left of the interview, you will see a little icon appear. Clicking that icon will take you to the Interview Kit. Just copy the URL from the address bar, and paste that into your interview invitation.
You can also access the link to the Interview Kit when you're on the Candidates tab. You'll hover your cursor just to the right of the candidate, and you will see that same icon. Clicking that will open a drop-down menu where you can select the interview for which you'd like to access the Interview Kit.