I have stated my business requirements several times

I have stated my business requirements several times and all I have so far is either incomplete or conflicting information.

I am selling nine courses as one "product" for one single payment.

I am also selling the same "product" for three monthly payments.

I need to link from an outside sales page (directly to a shopping cart.)

I've stated these business requirements several times but I keep on getting conflicting advise about how to set this up.

What plug-ins do I need and exactly how should they be configured.

PLEASE examine my exiting set up and reply with clear and concise step by step instructions, with screen prints.

I am new to this platform and I really need your help.

Time is of the essence.