If you are artistic then do this lesson but if you have no skills in this regard then I suggest that you use some of the free logo designs you can find here. But if you do have some artistic chops then why not design your own logo.
Here is a guide to podcast logos that you should check out first.
Once you've read the guide you should be able to create a brief: What things must your logo have?
Step 1
Brainstorm ideas for your podcast, what are some images that are related to your themes and ideas that will convey the topic of your podcast clearly?
Step 2
Find examples of logos that you like. Make a list of techniques and things that you like about the different logos.
Step 3
Create some mock-ups of possible logos.
Step 4
Typography - either take an existing font and adapt and change it for your logo or create your own using Adobe Illustrator.
Step 5
Colour schemes - try 5 different colour schemes
Step 6
Get feedback - Ask people what they think. Make changes and adapt until you have a logo you are happy with.
Teacher's Notes
91445 Use drawing to demonstrate understanding of conventions appropriate to design
91450 Systematically clarify ideas using drawing informed by established design practice