To enjoy the full speed of the Fantastical workflow, you'll want to take advantage of its keyboard shortcuts. The most important one is the shortcut that will open the Mini Window. By default it's Control-Option-Space, but you can change it to whatever is the most comfortable for you.
Open Preferences and switch to the General tab. Near the bottom of the window there's an option titled Mini Window keyboard shortcut: with a button to the right showing the current shortcut. Click the button and then press the combination of keys you'd like to use to trigger the Mini Window.
Now you can press your keyboard shortcut at any time, in any app, and open the Mini Window to immediately start entering a new event.
There are many keyboard shortcuts available to speed up your workflow. See the Keyboard Shortcuts section for more details.
Fantastical goes beyond just allowing you to choose which calendars are visible by offering "Calendar Sets." These sets allow you to create different collections of calendars and quickly switch between them, allowing you to view only what's pertinent at any given time.
When first opened, there is a Calendar Set called "My Calendar Set" ready for you. Check or uncheck calendars in the list as desired, or begin by adding a new set right away.
To add a new set, use the "+" button at the bottom of the left pane. Select a set in the list and its available calendars will be displayed in the right pane. Check or uncheck calendars on the right to determine their visibility when the set is selected.