The basic action is simple - if you're using Ethnio Scheduling, click anywhere on your calendar to add an open interview time.
The default will be 1hr, but what about if you want to add a time that's a different duration? To do that just grab the bottom of the time and drag up and down. Ethnio will remember that duration and if you click again all the spots will be set to that. Like this:
The shortest is 30min, and the longest is 8 hours. Now let's say you want to bulk add a bunch of times. You can either click the green plus, or click and drag around the empty range you want to create times:
Then set the options in this dialogue: