Simply join the community (there will be a 'join' button on the Homesteading Community Page). Next time you create a post, there should be an option near the 'Title' box that allows you to post into a community. Once you've joined, Homesteading community should appear in a drop-down list on that option.

There is also a 'write a post' button near the top of the Homesteading Community page.

Let me know if you have any other questions!