First of all, you have to move the point to a newsgroup to read articles in it.
The command j (
gnus-Group-jump-to-group) reads a
newsgroup name interactively, and moves the point to it. If there is no
such newsgroup in the buffer, a line for the newsgroup is inserted at
the beginning of the buffer.
The command r (
visible newsgroups to the current region specified by the point and the
mark. This is useful if you want to concentrate on a restricted set of
newsgroups in a region. Type C-x w (
widen) to remove the