Try accessing it on another computer. Then, let us know whether found the option in the profile settings to add an avatar.
And, can you post a screen shot of what you see? And, state EXACTLY, STEP-BY-STEP, how you trying to access the profile options. What URL are you going to, to log into your forum account? Then, what link or button do you click on? Then, what next, etc.? Without precise details here, I doubt any progress can be realized.