There are two essential things you need for a podcast; a mic and Audacity.
Audacity is a free software download you can install on any computer. After you have installed Audacity you can then record using a mic with a USB port.
After recording, save the podcast to a folder. After saving the file you then must export the file as a MP3. To convert the file follow: Audacity-File-Export As MP3. You will be asked the first time to locate the lame.enc.dll file. You only need to do this the first time.