There really is no effective way to place images alongside text in a blog style website that will consistently display correctly.

This is a limitation of web coding which may be fixed one day in the future, and is not any fault on the part of postach.io or Evernote.

It is possible to use tables to organise how images are displayed alongside text, but this does not always display correctly on a desktop of laptop browse, and will always come out wrong on a Smartphone (mobile phone or cellphone), and often will display badly on a tablet too. It it easy to check how a web page will display on a mobile device simply by pulling the browser to a narrow size. The page will re-arrange itself depending on the theme chosen and will automatically present the best display for a mobile device.

In any event, use of tables is deprecated in the latest web coding standards anyway.

The only option really is to place the image below or above text. If in doubt, select the Simplify Formatting option from the Format menu in Evernote.