Creating curved text is somewhat difficult in Paint.NET. One way to do it, is to select each letter of the text using the selection tool, then rotate and move it a little. However, the amount of time this would take with longer texts is just to much. The preferred method is currently to use a Plugin.
To learn how to install plugins see: Installing plugins in Paint.NET
The plugin we are using is called SpiralText, and can be downloaded from PDN's plugins forum here.
Curving text using circle text plugin
The circle text plugin can be used to create curved texts, which can be useful for logos. Note. This assumes you have already installed the plugin.
After installing the plugin you can add the curved text by using the plugin in: Effects-Text Formations-SpiralText...
At this point simply adjust the different settings until you get the result you want.