how can you put letters in gimp??
like SFHS like that so i can put my name in my head

On the toolbar, there will be a "A" somewhere. Click it, and go wherever you want to make the text on the head, and draw a rectangle around it. Type in the words or whatever you want there. You can also change colors, make it multicolored, change fonts, change sizes, and change the way it's facing like it can be mirrored, flipped, whatever you want.

tl;dr, look for an "A" somewhere in the toolbox.

hmm i trid that but i want a color

You can change the color (like if you are changing the colors of your paintbrush) before you type the text and it will automatically change to that color. If that doesn't work, highlight your text, and choose the color.