if you just want news, you don't need to setup alerts. Just turn on news on SETTINGS/DATA SOURCES/NEWS - for whatever sources you have access to. MT will automatically get the news and will show a bulb next to a symbol when it gets new news.
The alerts mechanism is for triggering other alerts on a subset of the news items. You don't have to specify the source unless you want the alert to only be triggered on news coming from a particular source. You can see the text of the source column on any news window.
Market Data 
Markets 
AI
