The St. Louis region has a helpful page to explain how to add calendars to your phone or PC here: http://stl.pca.org/add-region-calendar/. This will also work for the LTR calendar with the following changes:
Our LTR calendar ID is: firstname.lastname@example.org
You can also get to it with this URL: https://calendar.google.com/calendar/embed?src=s52gdanf8jvh397ak62i9d2ars%40group.calendar.google.com&ctz=America%2FChicago
You can also scan this with your phone:
When it opens on your phone, click the link at the bottom right with the + sign.
I have added Chicago Region PCA and St. Louis Region PCA calendars to our website as well. They show up in the Central Illinois Car Events calendar on our home page.