Help with point to point network

Im new to the wireless world. I have setup a few wired applications before but slowly trying to understand the use of wireless for use around the farm.
Ive googled for a few days and feel more lost then before i started.

I dont have ideal conditions the worst interferance ill be having is going threw bushy trees. I can see the building threw the shrubery but just barely. The trees are located almost center of the 1 mile distance. Though if need be i may be able to chainsaw a clear path threw them but want to avoid it since there protecting a ditch bank. The rest is open flat fields with only one 3 ft step up in elevation to one of the buildings

Im planning on using 2 of these for 1 mile apart buildings. http://www.hyperlinktech.com/web/hg2414d.php
What i dont know is what supplys ill need. I know i need antennas but what else do i need to gaurantee a successful setup? Also how do i go about aiming them accuretly?
Ill be using it to share internet and do some light gaming on the side
Thanks