Dialog window will open. Creating a MP3 is one of the options.
Burn your mp3 to CD in iTunes
If you're going to put it on a CD, the last thing you want to do is bounce to MP3. Doing so needlessly reduces the quality of your track. Does anyone give a damn about quality any more?
To answer the question:
First, set the green cycle selector at the top over the bar numbers in the arrange window to start/finish around the start/finish of the track you want to bounce. You also want to make sure no one particular region on a track is selected, otherwise that's all that's going to bounce.
Secondly, click File, Bounce. You want to bounce as PCM, format AIFF or WAV, 16 bit, sample rate 44100, with dithering enabled, file type interleaved.
Burn the resulting file to a CD, and you're golden.
