WarpOS isn't an OS in it's own right - it's an extension to OS3.x to run Power PC Applications. Assuming the previous owner had everything already installed then you can just boot your machine into Workbench as normal and try to run a PowerPC application such as the Voxelspace demo. If it runs then you know it's all installed OK.
If not then just install WarpOS from the OS3.9 CD using the installer. It will ask you to select what type of PPC card you have and then install itself automatically.
For MorphOS there is a guide to installing (you can either install it to HD or run it from CD) at the
MorphOS for PowerUP home page.
