You have to either
1. Get an updated version of the script
2. Find and correct the problem areas yourself
3. Add the line
error_reporting(E_ALL & ~E_DEPRECATED);
to the top of index.php, install.php or whatever specific page is causing the message. This "hides" the problem, but the script should run (at least until a new version of PHP goes from 'deprecated' to not working period).