As I recall, Cray uses the Suse distribution, with mods for processors. The programming environment should be the same as the standard Suse.
The first problem you will have is making sure that the required libraries are available. For that you will have to look through the OpenFOAM documentation for the list. Then find out whether these can be made available, or if you have to build them first as well.
One problem you might have is that OpenFOAM will not have been modified for the attached processors that may be on the Cray (not sure which one you have, nor is it required to be on it at all). These added processing elements are really fast... (they used to be Xilinx based).
Other than that, it SHOULD be no more than installing the source, a ./configure (with some library references), followed by a make command.
If this is to be installed for general use, you will need an admin to do a "make install", but it is possible to even build with defaults specified so that only a tar file used by the admin can install in the /usr/local directory on the various nodes.
OpenFOAM has been ported to the Cray XT-4 and 5 systems. Depending on who you work for (organization wise, if you work for the site then this might be possible), you might be able to get a version already built.