Buying a Champ

Hey, I just got and i tried to play him in Team Builder and he didn't pop up as a character, so i typed in the search and nothing came up. So i logged out and logged back in to see if that would work, it did.... but when i when to push find team it said that it was an invalid champion. And I also tried , , and many more, i it worked. I just want to play some so if you can help me that would help alot.