Drag and Drop from iTunes
If you have both Ringtone Expressions and iTunes open, then from iTunes you can simply drag a song into Ringtone Expressions to create your ringtone.

Drag and Drop from Windows Explorer
If you have Ringtone Expressions open, you can open your music library in Windows Explorer and simply drag a song into Ringtone Expressions to create your ringtone.

Right Click to Create Ringtone
In your Windows Explorer, you can right click any .MP3 files and select “Create a Ringtone with Ringtone Expressions ”.

Right Click From inside iTunes
In iTunes, your can right click a song and select "Show in Windows Explorer". Once shown, you can then either right click the song and select "Create Ringtone" or if you already have Ringtone Expressions open, you can just drag the song into Ringtone Expressions to create your ringtone