Parse error: syntax error, unexpected T_DOUBLE_ARROW in /viewtopic.php on line 1072 (or something close to 1072)
This is from an installation error.
When a mod says After Add, it means you add the code on the next line after the line after the last line in the find command.
To fix this error you will need to load your backup of the viewtopic.php file and retry installation on that file, keeping in mind the last thing I said.