1) Install FSX (I suppose it is !)
2) De-zip FSUIPC.zip in a folder on your disk
3) From this folder, right-click on InstallFSUIPC4.exe and select Execute as administrator, left click. Installation of FSUIPC completes, answer yes at several trustee requesters.
4) Open your FSX folder (typically C:\Program files\Microsoft Games\Microsoft Flight Simulator X\ ) and right click on fsx.exe.
Select Execute as administrator and left click.
Answer yes to any trustee requester.
5) You're done !
6) In FSX screen, on the menu bar, you must have an Add-Ons tab, open it, FSUIPC must be present. You can now enter the registration keys for FSUIPC and WideFS. Then close FSX and restart it.
Hope this helps.
Pierre Néel LFBE