Please provide at least the credentials for your (first) Tumblr account. Yes, I know - it would be great if the Tumblr API would allow us to directly upload photos for text posts (as we are used to by the web interface). All I can do for now its to encourage you to kindly (!) write to the Tumblr support to request that feature :-)
So - if you want to easily insert images into your posts you need to provide your FTP server credentials as well. If you don't own one yet - Google will present you with a lot of free services.
And even better - myTextPosts supports CloudApp (free/pro) - means you can easily insert/upload photos with your CloudApp credentials.…
Tumblr Account Credentials Hints:
Web URL formatting: http://example.tumblr.com (needed for preview)
Blog formatting: example.tumblr.com
FTP Account Credentials Hints:
Server: ftp.domain.com (for example: g2345.stratoserver.net)
Web URL: http://domain.com/path_to_folder (example: http://myownapp.com/tumblr)
In case of any trouble - please check this settings first!