Arial is a typeface family comprising standard Arial (Arial Std) and variants, including Arial Black, Bold, Extra Bold, Condensed, Italic, Light, Medium, Monospaced, Narrow, and Rounded.
If you want to used at silex, you need to copy the font swf to the folder: silex_server/fonts, and active the font at the silex manager or at the file silex_server/contents/conf.txt.
Mode Silex Manager:
You need to change the parameter FONTS_LIST at the file silex_server/contents/conf.txt:
You can download the source Arial Fla here: Arial-fla