Hello. I have always used the 125 kbps bitrate in MP3 exporting. I would like to change it, but there aren’t export options after I click on export. How can I change the bit rate? Thank you 
You need to click the “Options” button: http://manual.audacityteam.org/o/man/file_export_dialog.html
Audacity defaults to 128.
Early versions of Audacity had the MP3 options under Preferences rather than Export > Options.
Koz
where is that option in the new version?
in a 2.0.x version of Audacity, Archivo > Exportar… , choose “Archivos MP3” in the drop-down box then press the “Opciones” button.
Gale