Portfolios are optional; they can be websites, images, or something that basically describes your past experience or skills. If you are referring to the question that mentions giving a summary of your experience, judging from what is said, that may affect your chance of being accepted. Please note that past zine experience and having a portfolio are not mandatory, but an explanation of your qualities, your reasoning for wanting to join, and samples of your work are.
The self-descriptions are just so you can explain who you are, what you like, and stuff like that! This will not affect your chances of getting accepted; it's only for the moderators to know, and if accepted, the self-description/bio can be changed later on!