Make a list of things you would like to write about, then start at the top. It can be a bit overwhelming when just starting out, but break it down into smaller pieces. I have a list I continually update and revise as I write my articles. Some have become longer than article length, so they have gone into reports. I have also broken some up into pieces, so they have become two or more articles (hence, my last two Hubs).
Good luck, and I'm so glad you joined our community! :)