Update my iMac with iPhone podcasts

I have many more podcasts on my iPhone than on my iMac. How can I update my iMac with the podcasts on my iphone? I am afraid if I follow the instructions for syncing my iMac podcasts with my iPhone, I'll overwrite my iPhone podcasts with the very limited podcast library on my iMac.

I also saw something about enabling iCloud for iPhone apps that I want to appear on my iMac, but I don't see any switches on my iPhone settings to do that.