In Agenda At Once, notes are RTF (Rich Text Format) enabled, which means that you can use formatting toolbar to highlight parts of text. Elements of the formatting toolbar are, respectively:
|▪||Font (text) color|
|▪||Align paragraph to left|
|▪||Align paragraph to right|
|▪||Bulleted / Numbered list (switch type by pressing Ctrl+Shift+L)|
It is also possible to paste pictures from the clipboard, but this is not recommended unless pictures are very small. For larger pictures and files it would be better to use attachments.