Hi George,
The ability to superimpose the GP LLJ coherent turbulence files on top of the TurbSim full-field files is not supported directly within OpenFAST or FAST v8 (this feature was supported in FAST v7, which uses AeroDyn v13). However, you had asked in a prior forum topic (Question regarding TURBSIM coherent turbulence and .wnd files - #2 by Jason.Jonkman) about superimposing the files and saving them into a single file for use in OpenFAST or FAST v8. As I mentioned in that forum topic, the CTWind tool can be used for that purpose.
Best regards,