If the remote control you bought newly is the original one; it should work without any problem. If it is a universal remote control, you should set it up with the set-up code to LG.
In case it is original number:
Check the remote control for its infra-red emission. Check it with fresh batteries. Check by pressing all the buttons on it; and see whether all of it generates infrared signal while pressing. If it is found OK, check and replace the infrared sensor inside the TV. If you wish to get some details; check the site linked here. It has details about how to check a remote control; by one among the post. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/
If the remote control is found OK; check and replace the infra-red sensor inside the TV. Contact any service technician.
In case it is a universal remote control:
Set-up (Programming) procedure is too much to type in here, and is not practical and it will differ brand-to-brand remote controls. If you wish to get more; check the sites linked here. It has set-up code list & set-up procedure to many popular brand remote controls. One among it has general set-up codes to check with TVs and other devices are given, in the order of the 'device's brand name list' in alphabetical order. Pull up older posts. Search the sites by type in the brand name to your device in its search box at the top right part of the display window. It will help you to find the document easily.