A:AnswerThe Slingbox will work with the LG 50" Class (49.5" Diagonal) 1080p Smart LED TV, Model # 50LF6100 but how you connect it will depend on which model slingbox you have. The TV itself has all the connections that you would need and if you follow the instructions that came with your slingbox you should be able to connect it. If you could please clarify what you mean when you say that you are not able to "add" sling to it would help us determine what the issue is...^IFV