You can configure the tabs that are visible by default at bottom of the dashboard. To edit the settings, login as admin and goto Administration > Configuration

Config-key	Values	Meaning
default.dashboard.tab	0,1,2	Which tab should be shown by default, counting starts with 0
dashboard.show.myrooms	0 or 1	If the MyRooms tab should be visible or not
dashboard.show.chat	0 or 1	If the Chat tab should be visible or not
dashboard.show.rssfeed	0 or 1	If the RSS-Feed tab should be visible or not
rss_feed1	http-URL	ATOM-Feed URL for the dashboard RSS Tab
rss_feed2	http-URL	ATOM-Feed URL for the dashboard RSS Tab

Changes are immediately online, no need to restart anything.