2 Questions – need help please!

I just installed the latest Classifieds Responsive Theme on my site at http://www.rentmystuff.sg

I have 1 question and 1 problem:
1. In the Permalink Settings page, I see PremiumPress Custom Slugs and with the Listing Slug Name and Category Slug Name fields already filled in.

Below this are the normal radio buttons for choosing a permalink format. So my question is, which do we choose? Or is it already defaulted to the PremiumPress Custom Slugs and we just leave it at the Default radio button, which is https://rentmystuff.sg/?p=123 ?

2. I can create a listing as an ordinary registered member, but when I try to edit that listing, I get a 404 error. How can I enable registered members to edit their listings? Do I need a roles and capabilities plugin to enable this?

I noticed that even as Admin, I am unable to edit any listings as a 404 error shows up with the following details:

This error (404 page not found) means that for some reason the page you are trying to load could not be found. It maybe that your permalink cache needs refreshing;

(click here to refresh your permalink cache now)
If the error continues check your website link is correct, disable your plugin’s and then clear your browser cache.

Note: You are seeing this page because you are logged into an admin account, normal website visitors will not see this message.

Please help me resolve these two issues. Thank you.