You are logged on now. UNICOS is a normal UNIX, that means, you should be able to do most of the things you are already familiar with from other Unices.
If not, search for Unix Tutorials in google and read through them.
Enter man commandname where you replace commandname with the command you want to see the manual page for.

Some useful commands (see man commandname for details)
vi sourcefilename.f for editing FORTRAN-77 source files
vi sourcefilename.c for editing c source files
cf77 for FORTRAN compilation and linking
cc for c compilation and linking
./a.out for executing the program