As I have no idea what "addon" you have found or what it is supposed to do I don't know how to respond.
The way to check to see if your PHP environment is set-up for larger file uploads is to run a phpinfo() program and inspect its output; if you have properly configured php.ini, for larger uploads, and your DOCman settings are less than that amount, you should not see this message. The "copy" may well have been successful, but it takes more than copying a php.ini file to your directory for it to be used to change your environment.
I don't imagine that whatever "addon" you used actually accomplished this in the DreamHost environment. To do this on Dreamhost, you should follow the instruction in the DH wiki (here, and/or here) and then run the phpinfo() program to see if you did it correctly.