Hi Hannah!!
Thank you!
Well,I made the banner but the text was already on the photograph.I do know how to make it though:
1.Open a new "white" image in gimp
2.Choose a big font (like Arial) and write your word so it fills up a lot of the banner in the color "Black"
3.Save it
4.Open an image and open the one you just made as a new layer.
5.Set it to "Screen"
Hope that helps!