Video instructions for Membership

Are there any detailed video instructions for Membership plugin set up, cause I am having a hard time following along, and since I have not used it before it is a bit confusing to say the least..

As the main thing I am getting is 2 subscribe buttons for each membership section I have?

Also, what is the difference between

Free subscriptions gateway
PayPal Express Gateway
PayPal Single Payments Gateway

The reason I ask is because I have a site I am building where they have a membership (3 different flavors), and for those that just want to purchase individual ebook lessons they can do so, but not under a membership.

Thanks