Try the following steps to see if you can access your profile to change your name.
1) Click on your name in the top right corner, to open a sub menu
2) Then click on Account Profile
3) Select Basic Info on the page it opens
There you should see your profile name, with an option to edit at the side of it. Once you have changed your name, you will need to log out of the site and then log back in. Hopefully, this prompts the site to change your details.
If you are still having difficulties, then I would suggest sending one of the community managers a PM, to see if they can further assist you.
If you're referring to changing your forum name, once you've logged in, select your avatar in the top right corner.
This opens up a sub menu, select account profile, this should open up the page with all your details.
If you scroll down the page you should see your forum name with an option to edit at the side of it.
You might have to log out after changing your name and then log back in for it to change.
Hope this helps.
No as in...I can't even log in until I provide my community name and re-enter my password
Were you asking what your current community username so you could change it like Tracy described? If so, it is listed when you click on Profile or even when just look at any post you've made, like this one. In your case it seems to be one of the default usernames:UCD_28186309214