imosflm

iMosflm is being distributed with the executable of Mosflm 7.0.7 included - so you should download a machine-specific version of iMosflm.

There is no need for a separate download of Mosflm, unless you want to run iMosflm on a different platform.
Select the images to work on, either via the entry in the "Session menu", or by clicking on the "Add images" toolbutton in the main window (images panel).