All Files in archive directory \root\portal\block\* have to be changed on 
(=>  $cpg_root_path = '../gallery';   /*** YOU MUST CHANGE THIS ***/  <=) 
to point to your Coppermine Gallery relative path. No other edits are needed as all settings 
will be collected automatically if CPG's configuration file once could be found. There is no
need to have the CPG database tables in the same database as phpBB3's.

Above setup does work for my site which does'nt mean it will work for you also.
 
Copy directory \root\ of this package to your forum root (retain directory structure).

When done five new blocks will be available in Portal's block management to add to your portal setup.

Refresh styles and cache when done!