Ok, that is it!!!
We will do this my way, and I call this the "ACADEMY"!!!
You follow every single thing, and you should be fine.
Go to GIMP.
Go to Files -> New.
Choose the Canvas Size that you like.
Now, filled that Canvas with Black Color.
Design your Background.
I'll let you do the designing, and such.
Now, duplicate that layer.
HOW???
Layer -> Duplicate Layer
Now, make sure that you are on the Duplicated Layer. If you are not sure just click the Top Layer that is in your Layer Dock.
After clicking that, put the text that you want.
Now, go to Files.
File -> Save As
Put the Name, and then put .gif after the name.
Then a Box should pop up.
Tick "SAVE AS ANIMATIONS".
Now, choose the speed that you want.
I prefer you use 500 or lower.
Then click SAVE.
This is the most basic guide for that...I hope you get it now...