Hi
Believe it or not, not all LCD TVs have a wall mounting facility, particularly some of the DVD combi's where the DVD mech is in the way of the standard TV chassis where the wall mount would usually be.
You can check a couple of things;
1. check in the manual for any mention of wall mounting.
2. See if there are already screws in the mounting holes. If there is an obvious square pattern of screws on the rear (probably 75mm square or 100mm square) then these could be the wall moutn fixings. Don't remove any screws if you're not sure.
3. Sometimes they put plastic bungs in the wall mount fixing holes, again see if theres any obvious patterns.
4. There may be a plastic cover to remove first, again, check the manual.
Other than these, it may just be the case that your TV isn't wall mountable.
Best Regards
Graham