The texture tab isn’t going to get the Image onto the Sphere as you have to add a Material First…and add the texture to the material…not as a texture in the texture tab ( think of the texture tab as being where you add noise or grunge, etc.)
Here is a quick example using a grab of your texture…NOTE: an added sphere will have a Polar UV Map that will look like a rectangle…one way to get the texture on is to do a quick Smart Project Un-Wrap and select a couple of rings to form the Iris, move, scale, and adjust the UV to fit over your Texture you created, add a new material in the Materials tab…and ASSIGN it…you can then Invert the selection Ctrl+i and add another material and assign that…
then just add your Iris texture that has been saved as shown in this node group…
J’ai suivi tes conseils et j’ai crée un uvmapping (smart UV Project), j’ai chargé une image (image de l’iris) puis j’ai beau appuyer sur le bouton Assign, mais rien ne se passe.
I was able to color the iris with the Assign button.
But what I would prefer is to color the iris with the texture above.
I switched to Shader editor mode, then connected the Image Texture node.
The problem is that the texture occupies the whole sphere.