OK I named a category no problem but I can't add anything to it. I clicked on the Help link and it didn't help. I can't find the "Access by Category" or the "Add Item" button that it talks about on the help link. Please help! Thanks.
My first guess is that you're going into the journal the wrong way. There are a few ways to get to the journal, but some ways will take you in to your journal the way other people would view it, and if you go in that way then you can't edit or anything. If you're going in by going to your member page and clicking on the "read Kiyzersoze's garden journal" link, that takes you to the wrong place where all you can do is view things. To get to it so that you can edit, click on the "My Tools" tab, then on the gardening journal link.
The second possibility is that you never got all the way through journal setup--you have to add at least one plant in one of your categories in order to complete the setup process. Once you've done that, then you should see the page the way you're supposed to. If that's not the case, it would really help if you could post a screenshot of what you're seeing, that might give me some other ideas.
There are two ways to add a plant to your journal, one is manually entering everything yourself (which is I suspect what the help button give you instructions for), and the other way is to do it from Plant Files as you just did.