uv tables are simply read into IMAGER by READ UV. The rest frequency to be used to compute the velocity scale is normally found in the table, but can be overridden using the READ /FREQUENCY option. By default, the whole table is read, but a subset of the channels can be read using the READ /RANGE option (with the velocity scale as above).
UVFITS file may even be read directly as uv tables, applying the same conversion methods than the fits_to_uvt script. However, this capability is still only partially supported. While it will work for basic (i.e. in memory) handling, full access to the uv data is only possible on the native format: this includes subset selection, as well as direct operations on uv data files through the /FILE option of many UV_... commands.