Add additional "Widget" or "Content-Box" on Start Page

Hello,

I would like to ask how I can change content of the start page e.g. the content of those two boxes (view Photos, View Blog). But my original question is how to add an additional box where I can add a nice looking text box below those 2 buttons where I can describe in 1-2 sentences what the purpose of that homepage is.

Thank you very much in advance!