You have to disable security settings first, cause it's blocked by all the browsers. After you do that you must go through a harsh process... I'll copy/paste the description of the process that helped me get to step 5 (still doesn´t upload, but that's a whole different problem than yours):
After reloading the page, this brought up a new 3D model with just my hair and nothing else. But in the background i could finally see the delete button (a bin icon) however it will still greyed out in the background because the generating gameface was infront of it and wouldnt allow me to click anything.
Here's where it gets a bit more tricky. I pressed the 3 horizontal lines in the top right of the browser to bring up the menu, and then went on more tools > developer tools. Inside the 'elements' tab, i could hover over each part which would highlight part of the page in blue. I then did trial and error, and deleted each line untill i finally found the part to delete where it gets rid of the generating gameface and allow me to press the delete button. If you delete the whole page, just refresh and try again.
It then took me to the 'are you sure you want to delete page' or whatever it is, and again i used the same method so i could actually click on the button to delete it and finally, my old gameface was deleted.
But the trouble sadly didnt end there. After uploading my photos, it would firstly show them sideways. For this, i just edited the photo on 'preview' on mac, by rotating till it gets to the right angle, even though it was already on this angle. But when saving the image as how it was anyway, i uploaded it again and it actually showed it the right way up.
Then on the next step, step 3, i couldnt even see my photo so i didnt know where to place the face template! And on step 4 my image would be either extremely zoomed in, or only a quarter of the image would show in the top left corner.
Luckilly, i found this link, which involved me clicking on the three horizonal lines again on chrome to bring up the menu, and zooming out to 25%, then zooming out on the slider of the gameface feature till i could see my photo properly. Heres the link - http://answers.ea.com/t5/FIFA-15/gameface/m-p/5390564#M203144
And yeah you guessed it, just as when i thought everything worked, it didnt. Upon saving my gameface, it kept saying error cannot save gameface. I got so frustrated i just kept pressing save gameface, said a little prayer and behold, it worked!
This is quite a long and frustrating process, and once again im sorry its not very clear and there isnt any screenshots, but i didnt expect to be writing this message. Hope it works for you guys