MyBB Community Forums

I have downloaded the plugin, the notes to which said put the files in the upload folder in the root directory. These included a inc directory with a plugin sub directory. Those already exist in the root directory so I just put the php file in the existing plugin folder. Nothing has changed.
I have added the coding to some of the templates as told in the other thread, but some don't have a form tag at all and only one has a revert to original option.
So I am completely confused.
Can anyone tell me where I am going wrong please?

Thank you, thank you, thank you. I am just starting my semester and have relied on this discussion board for years. I upgraded MyBB a few days ago - and for the first few days was working great. Then, I started getting the login error - and panicked. This was the quick fix I needed for my students who are just getting started.