If you have the Steam version, just reinstall it. If you have a disc version, search for the "SFxT official GFWL removal patch" on Capcom’s support site or use xliveless from its official GitHub repository. Do not trust random DLL download sites.
I understand you're looking for a guide on the xlive.dll file in the context of Street Fighter X Tekken . However, I must first provide a critical warning before proceeding. Street Fighter X Tekken Xlive.dll File Download