With difficulty :) It's the real name of Sitting Bull, right? I'd do my best not to completely Anglicise it and go with: Ta-ta-kay-a Ee-yo-tar-kay. But I have no idea if that's anywhere near how it should be pronounced.

I agree with Paul - I'd also try to pronounce it as phonetically as possible, but the stresses might still be out: Ta ta KE a I yo TA ke An anglicised version might sound like "Ta ta KEY a Ay yo TAH ki".