To actually set up frame-relay on Linux, you will need a frame relay card, and you'll need to make sure your kernel has the modules that support that device. If you have those devices, then your kernel should already see them, and you should be able to plumb them and configure them per the documentation for the devices you have.
If you don't have an actual frame relay card (not to mention a switch or router capable of terminating that connection), then you might want to look into Dynamips / Dynagen / GNS3.
Think of it as Virtualbox for network devices. You can set up virtual networks, which include frame-relay interfaces, with your vms running real IOS images.