Like other raster images, registering a SPOT image involves choosing a coordinate system and assigning at least three control points in the Register Raster Image dialog box. Before doing so, you must gather the appropriate information from settings in the image's .HDR/.REP files.
If you open a SPOTView™ image's .HDR file using an ASCII editor, you'll see that it contains settings like the following. The settings for your image will likely differ.