Size of MP3 file exported

I have just created and exported a narration file (stereo) along with a music mix. The file is just 20 minutes long, but is 236 MB size. This seems very large, is there a way it can be a smaller size, for ease of transferring to others ?

Windows 7 system
Audacity version 2.0.2
Thanks Mildred

If this is a stereo file, then you have probably exported in WAV format (or another uncompressed format) and not as MP3.

See here for how to set the file export format: