Taking a leap of faith here given that you have not explained which questions on which page you are talking about:
If you use the Generate Key/CSR function, please note that you must fill in ALL fields, including those that do not apply to you (you can just enter NA in them). If any fields are empty, the key and CSR will not be generated.
If you just want to get an SSL certificate, like you said, then you do not need the Generate Key/CSR functionality. The client area will provide you with a private key to upload instead, so you don’t need to generate one yourself.