Authorize.NET step-by-step?

I'm having problems getting the Authorize.NET gateway to work with the Membership plugin. I get to the subscription page but there is no submit button or link to click to select the subscription.

I have seen other posts that suggest I need to install a cert for SSL, but no documentation on the whys and wherefores for this.

I've seen other posts that suggest that once you see the credit card form there is no submit button, but no answer to this either.

I have also filled in the gateway info as best I can but the only options I understand are the sandbox, Login and API Key fields ... I'm hoping the remaining defaults will just work?

I am using the latest plugin (2.0.6).

Can someone who has gotten this working from end-to-end point me to a reference that describes how to configure and troubleshoot this integration?