This is very easy
1. Translate the language files and place a directory in your languages directory called arabic with the files which are translated
2. Open your pp-inc.php file and find these lines at around 274-276 and save when done
elseif ($Globals['pplang'] == "chinese") {
$contentmeta = "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=gb2313\" />";
}
add below this these lines
elseif ($Globals['pplang'] == "arabic") {
$contentmeta = "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=iso-8859-6\" />";
}
3. Open config-inc.php and change $pplang from english to arabic
4. If you have made the changes above and uploaded those files you should have arabic languages displayed
PS . As far as right to left this just depends on how you translate the strings
EXAMPLE
if a string is I have a big black dog in arabic you would translate that string the proper direction and we will display that language string the way you make it