you just need a good text editor (notepad++) as editor for your mxml and download the flex sdk.
but if daghan wawarts imu company, request ug flex builder coz gepadali jud imung kinabuhi ana..hehehe
pwed gamit kag ant for building your mxml (try tan-aw sa manual sa flex sdk coz the provide a sample)
then embed your build output (swf) sa imung webapps.. daog na dayun