hello UGrians, im wondering what can i do to lower the action of my acoustic guitar.

i have a plastic saddle which looks something like a stick which can be taken out.

so how can i lower it?? do i have to send it for servicing?? if i send it for servicing, would it be expensive?? i think that plastic saddle is the one causing the high action.. if im wrong please correct me..

my acoustic guitar model is a Fina FD 801C BK. please help.. and im sorry if this was posted in the wrong forum. thanks.
oh thanks for the info tom. but... i've already taken out my rusted strings.. and i cannot measure the distance between the fretboard and strings now.. what do i do??? btw just a quick question, can i just replace the saddle?? with a shorter ?
Yes, in fact replacing your saddle with a better quality one is recommended. Bone is by far the best value for money. It will almost certainly improve your guitars tone and sustain. There are better quality materials but they get pretty pricey whereas a bone saddle blank can be bought for roughly $10. Its a relatively simple job you can do yourself but even easier to take it to a qualified tech and tell them exactly what you want.