1. Select a topic in the tree.
2. Move a cursor to a place where you want image to be placed.
3. Enter pseudo-tag as follows:
{%IMG yourimage.ext%}
where yourimage.ext - is a full name of your image with extension.
Also you can insert library images in full-size. Place cursor where you want to library image to be, right-click, select "Insert Library Image" and select an image from the list.