Help is here!
All right, so - during the sections you're describing, you actually need to select one (or more) segments under each of the sentence fragments.
That would look like:
I am a poster.
You might select poster, and some dialogue would appear:
"A poster, as in I post on online forums..."
"A poster, as in I'm an object stuck on the wall."
You'd click the latter, and that might work enough as a half-truth to turn the submit button black, which means it can be used. It can take awhile to get used to, but just keep in mind the nature of J, and you'll be humming along in no time!