Insert macro "NewsStoryRollupByMostRecent" into your main text area. The button to insert macros is located at the top of the main text panel and is 6th from the right. This will open up a new panel at the right of the interface and has a drop down you can choose your macro from.
Once the Macro gets inserted, it will open up a new panel in the left which will prompt you to choose a directory to pull content from. Simply click the "add" text, which will open up a new panel displaying the entire Umbraco file system. Simply click on the directory you want to pull content from and click submit near the bottom right of the panel.
If you do not have a directory set up to pull content from, we can create one. Hover over the name of your content page in the content panel located on the left side of the Umbraco interface and click the three dots that show up. This will open up a new panel which will contain a "content page" line near the top, click on that line. We wont do much with this content page as it is simply the parent node of the directory we are pulling content from. We will want to give the page a name though, there is a field near the top of the interface that has some greyed out text which says "Enter name", click on this field and lets name the page "Roll up Content". After you enter a name, click the "save and publish" button near the bottom right of the screen.
Repeat step 8 above except we are going to click the three dots to the right of our new "Roll up Content" page and instead of creating a "content" page, we will want a "News item".
Give your news item an appropriate title, body text, and then save and publish. Once this is done the macro you previously created will automatically pull that data from the news page and generate a corresponding news item for it's page.
Repeat steps 9 & 10 until you have all the new's and announcements you want to display.
Pat yourself on the back, you just created an announcement page.