Hey there. First off, welcome to HIVE! It's always a pleasure to greet newcomers. I remember the post you referenced. It describes how to use tags on the Esteem App when you want to post to a community.
It's easiest to join those Communities and also easy to post to them on Peakd. On Esteem, you have to put your first tag as the community number (found at the bottom of each communities about page).
If you're having issues posting using the esteem app, my guess is it's a tag error that is preventing the action.