The database credentials need to be stored in
db/local.php so the first thing probably is to try to use the username, password and database (and host) in there to make a connection in the command line (or something) - can't remember how Tiki 1.x handled errors like that, so i'd guess it just can't connect.
Once you can connect add those to
db/local.php like this:
$host_tiki='localhost'; $user_tiki='databaseuser'; $pass_tiki='databasepassword'; $dbs_tiki='databasename';