BlogPress does not have a smartphone app. We are in no way associated with the BlogPress app. That's just a bit of very unfortunate naming. :0
Instead, we recommend the FREE app provided by WordPress.
More info here: https://apps.wordpress.org/
Here are the detailed setup instruction for iOS and Android devices
Frequently Asked Questions - https://apps.wordpress.org/support/
Here's the summary...
Step 1: Go to the app store and download the app
Step 2: Once it's installed, open the app, click on the link at the bottom that says "Add Self Hosted Site."
You do NOT need a WordPress.com account to manage your BlogPress blog - do NOT attempt to login to WordPress.com or the connection will fail. (That's the one confusing part about the app setup :))
Step 3: And then enter the following information.
username: your blogpress username
password: enter your blogpress password here
URL: Your BlogPress blog address (e.g. http://myblog.theblogpress.com)
Step 4: You'll then see your site - just click on the name of the site and you'll be able to write, edit, preview, and publish posts.
When you're in the actual post editor, you'll see a link at the bottom right to add images.