An editorial calendar is basically a roadmap of what you want to make and when it will be going live. You should fill it with specific items - even if you haven't developed them yet. The objective is to have a clear roadmap to work with for the next year.
Try to think outside of the box when looking for original ideas you and your team can try out on social media. Consider important holidays and events that large (or smaller) groups of people will be participating in anyways nationally or even just in a few specific cities.
Use the worksheet attached to come up with at least 10 blog post titles or other content ideas you could do to be unique and build your roadmap.