Hi, Sara.y -
In other words, what hurry_hui is saying, is that you usually don't have to do *anything*. The SuSE 11 installer should detect if you have multiple CPUs, and should generally install the SMP version by default. It's easy to check (including the method hurry_hui gave you).
If, for whatever reason, you *don't* have SMP (and, of course, if your system is actually multi-core or multi-CPU), then it's easy to add: simply go into "Yast":
'Hope that helps .. PSM