There's a tutorial for the CS 757 FMC here. The 757/767 FMC is pretty similar to the 777 one, so you should be able to operate the 777 FMC by most of these steps. Also, you can take a look at some of the tutorials for the 737NG by either of the two recent producers of that product, as the 737NG FMC is nearly identical to the 777 one, at least as far as I've seen.