Download the programs Audacity and LAME MP3 encoder (see Resources). If you already have LAME MP3 encoder then update to the latest version. These programs have different versions for Mac or Windows computers.
From the LAME zip file, select the file named "lame_enc.dll". Save this file on your hard drive in a place that is easy to find. Do not open all of the files that come with LAME MP3 encoder.
Open the Audacity program and select the MP3 that you want to split. Select the file from where it is stored on your computer. Make sure that the selection tool button is highlighted in the upper right corner of the screen. This button looks like an uppercase I.
Select the spots where you want to split the MP3 by using the cursor counter. To separate the first minute, highlight the area from 0:00:00 to 1:00:00. With the section highlighted go to the edit menu and select copy.
Create a new track by selecting new under the file menu. Then under the edit menu select paste. This will paste in the first minute you highlighted from the original MP3.
Export the new shorter track by selecting export as MP3 from the file menu. The first time you do this you will need to specify where you placed the LAME file from step 2. Choose where to save the new MP3 and name the new music file.
Repeat steps 4 through 6 until you have split the MP3 track into the number of chapters you want. This time start your new highlighted section where the previous highlighted section ended.