How to install window

[block]

We have a concrete block wall. If the exterior is primed and painted then could someone tell me if the buck board should be flush with the exterior ?
If so then how do I protect it or cover it up ?
What are my options ? Please give name or type of product or some kind of description so I can look it up on google search. I have no prior experience so any help would be great. I'm not going to install the windows myself I just want to investigate different product solutions and purchase them for installation.
Thanks

[block]

Well I stopped by Lowe's on the way home yesterday and was educated some on what to use around windows. I believe I'll be using a solid pvc trim against the window along with a solid pvc brick mold attached to the outside of that.
Thanks