Coloring a texture in SDL2

[Manuel Di Criscito]

I develop games using c++ and sdl2 and in this topic i'll try to give more informations possibles about my problem.
I have a texture 11x11;
A square colored red.
This texture is the skin of the main character.
I created the skin creator: so a board 440x440 divided in 121 squares (11x11=121) where the user draws his skin with all colors.
Ok.. simply i want to use the skin created in game. So this drawing (that contains data structures about x, y and color of all squares)
Should become a texture 11×11.
I was thinking i could use locking texture and draw on it but there are a lot of errors and i don't know how to use those variables like "format, access, flags" etc.
Can someone explain me how to do that?
Please
Thanks