This wizard will configure a news gateway: your server will be able to fetch newsgroups from an external news server (usually your ISP's, named something like news.domain-of-your.isp) and make them visible to your internal network. Therefore the first step is to specify which external news server you want to use.
Then you need to specify the interval (in hours) between each refresh. You need to find a balance here: specifying too high an interval might make your server's news obsolete rapidly while specifying too low an interval might elevate your server's (inter)network load considerably. Of course, all will depend on the traffic of the news sites being mirrored and the Internet connection speed of your server.